delivered the opinion of the court:
On June 13, 1963, the legislature approved an amendment to section 10 — 21.3 of the Illinois School Code relating to the duties of school boards. (Ill. Rev. Stat. 1967, chap. 122, par. 10 — 21.3.) This amendment, commonly called the Armstrong Act, provides in part: “As soon as practicable, and from time to time thereafter, the board shall change or revise existing [attendance] units or create new units in a, manner which will take into consideration the prevention of segregation and the elimination of separation *595of children in public schools because of color, race or na-: tionality.”
On August 4, 1965, the plaintiffs, seven children, by their respective parents, instituted a suit in the circuit court of Lake County claiming that the Waukegan City School District had violated the Armstrong Act and seeking a. mandatory injunction requiring the district to revise the boundaries of its school attendance units. The district and the local board of education were named as defendants.
No boundary changes had been made in the school district since the enactment of the Armstrong Act. At the time suit was filed, the percentages of Caucasian and Negro students in each of the district’s attendance units were as follows:
Name of Percentage of Percentage of School Caucasians Negroes
Whittier 15% 85%
Clearview 100% 0%
Glen Flora 98% 2%
Glenwood 100% 0%
Hyde Park 100% 0%
After suit, had been filed, Dr. McCall, who was then the superintendent of the defendant school district, was requested by the board to make a study of the Whittier and surrounding attendance units. Dr. McCall prepared a comprehensive report, which included four possible revisions of the boundaries for the school district area, which were designated plans 1, 2, 3, and 4. His observations concerning each plan’s feasibility and desirability were part of the-, report. On June 13, 1966, the board considered the report, which, though it described possible boundary changes, recommended that no changes be made, and voted to make no revisions of attendance unit boundaries.
Trial was had on the plaintiffs’ complaint and at its conclusion on July 20, 1966, the court found inter alia that *596the racial imbalance in the Whittier School area had not been created by any deliberate conduct on the part of the defendants and that the defendants had not been guilty of any intentional racial discrimination. Also, the trial court held' that the Armstrong Act was constitutional and applicable to “so-called de facto segregation in schools, i.e., racial imbalance in schools not created by the deliberate intent of a school board.” The trial court judged that the defendants’ failure to make any change in the boundaries of the district’s attendance units was unreasonable under the circumstances and in violation of the Armstrong Act. The court therefore ordered the defendants to submit a plan making reasonable boundary revisions so ás to..“in .some measure ameliorate the racial imbalance” in the attendance units concerned. August 4, 1966, was set for a hearing to consider the plan to be proposed.
On such date the trial court incorporated in its decree plan 2 of the McCall report with certain modifications. These modifications were proposed by Dr. Van Devander, the new school district superintendent, to improve the original plan 2 by avoiding certain traffic hazards and by more acceptably balancing class loads among the schools. Under the court’s decree the distribution of Caucasian and Negro school children in the district was to be:
Name of School Percentage of Caucasians Percentage of Negroes
Whittier 57-4% 42.6% .
Clearview ..100% 0%
Glen Flora §3% 17%.
Glenwood 83.6% 16.4%
Hyde Park 79.9% 20.1%
In this direct appeal the defendants challenge the constitutionality of the Armstrong Act, alleging that the Act’s requirement that race be considered as a factor in changing or forming school attendance unit boundaries, constitutes a *597racial classification comdemned by the equal protection clause and due process clause of the fourteenth amendment to the United States constitution and the due process clause of the Illinois constitution.
To support this claim, the defendants heavily rely on three Federal cases, each of which held, no State law being involved, that a local school board does not have an affirmative constitutional duty to act to alleviate racial imbalance in the schools that it did not cause. (Deal v. Cincinnati Board of Education, (6th cir. 1966) 369 F.2d 55, cert. denied 389 U.S. 847, 19 L. E. 2d 114, 88 S. Ct. 39; Downs v. Board of Education of Kansas City, (10th cir. 1964) 336 F.2d 988, cert. denied 380 U.S. 914, 13 L. Ed. 2d 800, 85 S. Ct. 898; Bell v. School City of Gary, Indiana, (7th cir. 1963) 324 F.2d 209, cert. denied 377 U.S. 924, 12 L. Ed. 2d 216, 84 S. Ct. 1223.) However, the question as to whether the constitution requires a local school board, or a State, to act to undo de facto school segregation is simply not here concerned. The issue here is whether the constitution permits, rather than prohibits, voluntary State action aimed toward reducing and eventually eliminating de facto school segregation.
State laws or administrative policies, directed toward the reduction and eventual elimination of de facto segregation of children in the schools and racial imbalance, have been approved by every high State court which has considered the issue. (Pennsylvania — Pennsylvania Human Relations Com. v. Chester School District, (Sept. 1967) 427 Pa. 157, 233 A.2d 290; Massachusetts — School Committee of Boston v. Board of Education, (June, 1967)-Mass. -, 227 N.E.2d 729, appeal dismissed, (Jan. 15, 1968) - U.S. -, 19 L. Ed. 2d 778, 88 S. Ct. 692; New Jersey — Booker v. Board of Education of Plainfield, (1965) 45 N.J. 161, 212 A.2d 1; Morean v. Board of Education of Montclair, (1964) 42 N.J. 237, 200 A.2d 97; California— Jackson v. Pasadena City School District, (1963) 59 Cal. *5982d 876, 382 P.2d 878; New York — Addabbo v. Donovan, (1965) 16 N.Y.2d 619, 209 N.E.2d 112, cert. denied 382 U.S. 905, 15 L. Ed. 2d 158, 86 S. Ct. 241; Vetere v. Allen, (1965) 15 N.Y.2d 259, 206 N.E.2d 174; see also Guida v. Board of Education of City of New Haven, (1965) 26 Conn. Sup. 121, 213 A.2d 843.) Similarly, the Federal courts which have considered the issue, including Deal v. Cincinnati Bocvrd of Education, (6th cir.) 369 F.2d 55, cert. denied 389 U.S. 847, 19 L. Ed. 2d 114, 88 S. Ct. 39,. relied on by the defendants, have recognized that voluntary programs of local school authorities designed to alleviate de facto segregation and racial imbalance in the schools are not constitutionally forbidden. E.g., Offermann v. Nitkowski, (2d cir. 1967) 378 F.2d 22; Deal v. Cincinnati Board of Education, (6th cir. 1966) 369 F.2d 55, 61, cert. denied 389 U.S. 847, 19 L. Ed. 2d 114, 88 S. Ct. 39; Wanner v. County School Board of Arlington County, (4th cir. 1966) 357 F.2d 452, 455; Springfield School Committee v. Barksdale, (1st cir. 1965) 348 F.2d 261; Hobson v. Hansen, (D.D.C. 1967) 269 Fed. Supp. 401, 509, 510.
In Springfield School Committee v. Barksdale, (1st cir. 1965) 348 F.2d 261, the school authorities of Springfield, Massachusetts, had passed a resolution to take appropriate action “to eliminate to the fullest extent possible, [de facto] racial concentration in the schools within the framework of effective educational procedures.” Addressing itself to this resolution, the Court of Appeals for the First Circuit stated at page 266 that: “It has been suggested that classification by race is unlawful regardless of the worthiness of the objective. We do not agree. The defendants’ proposed action does not concern race except insofar as race correlates with proven deprivation of educational opportunity. This evil satisfies whatever ‘heavier burden of justification’ there may be. Cf. McLaughlin v. State of Florida, 1964, 379 U.S. 184, 194, 85 S. Ct. 283, 13 L. Ed. 2d 222. It would seem no more unconstitutional to take into account plain*599tiffs’ special characteristics and circumstances that have been found to be occasioned by their color than it would be to give special attention to physiological, psychological or sociological variances from the norm occasioned by other ' factors. That these differences happen to be associated with a particular race is no reason for ignoring them. Booker v. Board of Education, 1965, 45 N.J. 161, 212 A.2d 1 * * *.”
In Morean v. Board of Education of Montclair, (1964) 42 N.J. 237, 200 A.2d 97, the Supreme Court of New Jersey sustained the constitutionality of a school board’s plan to assign students from a predominantly Negro junior high school to the town’s three remaining junior high schools, even though race had been a consideration. The court stated there that: “The motivation was, to avoid creating a situation at Hillside [school] which would deprive the pupils there of equal educational opportunities and subject them to the harmful consequences of practical segregation. Constitutional color blindness may be wholly apt when the frame of reference is an attack on official efforts toward segregation; it is not generally apt when the attack is on official efforts toward the avoidance of segregation.” 200 A.2d at 99; accord, Offermann v. Nitkowski, (2d cir. 1967) 378 F.2d 22, 24.
Also pertinent is the observation of the Supreme Court of Pennsylvania in Pennsylvania Human Relations Com. v. Chester School District, (Sept. 1967) 427 Pa. 157, 233 A. 2d 290. In this case, which involved de facto segregation in public schools, the court said: “The School District does not suggest that it would be unconstitutional for the Legislature to command them to consider race in their redistricting proposals in order to achieve a semblance of racial balance in its schools, nor do we believe there would be any merit in such a contention.” 233 A.2d at 294.
Too, the United States Supreme Court on January 15, 1968, dismissed an appeal in School Committee of Boston v. Board of Education, (Mass. 1967) 227 N.E.2d 729, *600which challenged the statute providing for elimination of racial imbalance in public schools “for want of a substantial federal question.” - U.S. -, 19 L. Ed.2d 778, 88 S. Ct. 692.
The test of any legislative classification essentially is one of reasonableness. This court stated in City of Chicago v. Yokes, 28 Ill.2d 475, that neither the fourteenth amendment nor any provision of the Illinois constitution forbids legislative classifications reasonably calculated to promote or serve a proper police-power purpose. “Rather, they invalidate only enactments that are arbitrary, unreasonable and unrelated to the public purpose sought to be attained, or those which, although reasonably designed to promote the public interest, effect classifications which have no reasonable basis and are therefore arbitrary.” (28 Ill.2d at 479; see Chicago Real Estate Board v. City of Chicago, 36 Ill.2d 530, 542, 543.) And, of course, the burden rests upon one assailing a statute or a classification in a law, to show that it does not rest upon any reasonable basis but is essentially arbitrary. Thillens, Inc. v. Morey, 11 Ill.2d 579, 591; Stewart v. Brady, 300 Ill. 425, 436.
Here, the legislature has directed school boards “as soon as practicable” to fix or revise the boundaries of school attendance units in a manner that “takes into consideration” the prevention and elimination of segregation. We cannot say that the legislature acted arbitrarily and without a reasonable basis in so directing the school boards of this State.
The legislature is necessarily vested with broad discretion to determine not only what the public interest and welfare require, but what measures are necessary to secure such interests. (Thillens, Inc. v. Morey, 11 Ill.2d 579, 593; People v. City of Chicago, 413 Ill. 83, 91.) We have said: “With the growth and development of the state, the police power necessarily develops, within reasonable bounds, to meet the changing conditions. The power is not circum*601scribed by precedent arising out of past conditions but is elastic and capable of expansion to keep up with human progress. It extends to the great public needs, that which is sanctioned by usage or held by prevailing morality or strong and preponderant opinion to be greatly and immediately necessary to the public welfare. City of Aurora v. Burns, 319 Ill. 84.” (People v. City of Chicago, 413 Ill. 83, 91; accord, Zelney v. Murphy, 387 Ill. 492, 500.) Too, not to be disregarded is article VIII of the constitution which directs the general assembly to “provide a thorough and efficient system of free schools, whereby all children of this State may receive a good common school education.” 111. Const., art. VIII, sec. 1.
When, in Brown v. Board of Education, (1954) 347 U.S. 483, 98 L. Ed. 873, 74 S. Ct. 686, the Supreme Court declared unconstitutional de jure segregation in public schools, it made clear its position that all segregation of children solely on the basis of race deprives children of the minority group of equal educational opportunities. Though Brown directly concerned de jure segregation, segregation caused by official governmental action, courts since Brown have recognized that de facto segregation has a seriously limiting influence on educational opportunity. Booker v. Board of Education of Plainfield, (1965) 45 N.J. 161, 212 A.2d 1, 4, 5, 7; Jackson v. Pasadena City School District, (1963) 59 Cal.2d 876, 382 P.2d 878, 881, 882; Pennsylvania Human Relations Com. v. Chester School District, (1967) 427 Pa. 157, 233 A.2d 290; Springfield School Committee v. Barksdale, (D.C. Mass.) 237 F. Supp. 543, vacated on other grounds, 348 F.2d 261.
The fact that children other than Negro children may be deprived of equal educational opportunities does not form a constitutional impediment to the Act concerned. The legislature is not required to choose between legislating against all evils of the same genus or not legislating at all. It may recognize degrees of harm, confining itself to where *602the need seems most acute. (Chicago Real Estate Board v. City of Chicago, 36 Ill.2d 530, 543-552; Stewart v. Brady, 300 Ill. 425, 436.) Too, the Armstrong Act would apply to the offensive segregation of school children of any “color, race or nationality.”
We deem that neither the fourteenth amendment nor any provision of the Illinois constitution deprives the legislature of the authority to require school boards “as soon as practicable” to fix or change the boundaries of school attendance units “in a manner which will take into consideration” the prevention and eventual elimination of segregation.
It is apparent from what we have said that our view is that the Armstrong Act was designed to apply to de facto school segregation. Illinois has never been classified as a de jure segregation State. School authorities in Illinois were forbidden from separating or excluding school children based on race or color as early as 1874. (Chase v. Stephenson, 71 Ill. 383; Hurd. Rev. Stat. 1874, chap. 122, par. 100 (now Ill. Rev. Stat. 1967, chap. 122, par. 10—22.5); sée also People ex rel. Longress v. Board of Education of The City of Quincy, (1882) 101 Ill. 308; People ex rel Peair v. Board of Education of Upper Alton School Dist., 127 Ill. 613; People ex rel. Bibb v. Mayor and Common Council of Alton, 193 Ill. 309.) In 1954, the United States Supreme Court in Brown v. Board of Education, 347 U.S. 483, 98 L. Ed. 873, 74 S. Ct. 686, declared de jure school segregation by State action unconstitutional. Since then the unconstitutionality of de jure segregation has been clear. It would be unreasonable that our legislature, in 1963, in enacting the statute here concerned would be directing its attention superfluously to de jure rather than de facto school segregation, as defendants maintain. (Accord-: Pennsylvania Human Relations Com. v. Chester School District (1967) 427 Pa. 157, 233 A.2d 290, 296.) We concur in the trial court’s interpretation that the reference in the Armstrong Act to *603the “elimination of separation of children in the public schools because of color” is intended to apply to de facto segregation.
Too, the appellants question whether the Armstrong Act is so imprecise- in defining a school board’s duty as to be unconstitutional.
The Act, revised section 10 — 21.3 of the Illinois School Code, (Ill. Rev. Stat. 1967, chap. 122, par. 10 — 21.3) does not refer to considerations traditionally relevant to the determination of school attendance unit boundaries such as classroom size, distances to school and traffic hazards. However, neither did the prior section 10 — 21.3 refer to these factors. It simply directed school boards then, as the present section does, to “establish one or more attendance units within the district.” (Ill. Rev. Stat. 1961, chap. 122, par. 10 — -21.3, as originally enacted see 1951 Laws of Illinois, pp. 591, 593.) The omission, if it be considered such, does not invalidate the legislation. “When it is necessary, the legislature may commit to others the responsibility for the accomplishment of the details of its expressed purpose. The scope of permissible delegation must be measured in terms of the complexity and diversity of the conditions which will be encountered in the enforcement of the statute.” (Department of the Public Works and Buildings v. Lanter, 413 Ill. 581, 589-90.) It is known that conditions certainly vary from school district to school district in Illinois and may vary within the same district. As we declared in a context resembling the present one: “It would be both impossible and undesirable for the legislature to draft rigid nondiscretionary standards which would embrace each and every school district boundary change, for conditions surrounding the changes are seldom the same.” School Dist. No. 79 v. School Trustees, 4 Ill.2d 533, 537-538; accord, Schreiber v. County Board of School Trustees, (1964) 31 Ill.2d 121, 126, 127.
We deem that the intention in the enactment was not *604to eliminate or minimize consideration by boards of factors traditionally weighed in setting school boundaries. Rather, the intent was to direct school boards in forming or changing school units to take into consideration color, race and nationality so that segregation of children on such basis would be prevented and, where appropriate, eliminated.
The Act does not designate when a school is to be considered racially segregated or imbalanced. However, this does not mean the Act lacks adequate specificity to be constitutional. (Accord: Pennsylvania Human Relations Com. v. Chester School District, (1967) 427 Pa. 157, 233 A.2d 290, 301.) A statute need not always define each of its terms and detail each of its procedures. “It is only where the legislative act is so indefinite and uncertain that courts are unable to determine what the legislature intended, or when the act is so incomplete or inconsistent that it cannot be executed, that the law will be invalidated by reason of indefiniteness or uncertainty.” (People ex rel. Drobnick v. City of Waukegan, 1 Ill.2d 456, 465; accord, People ex rel. Christensen v. Board of Education, 393 Ill. 345; Husser v. Pouth, 386 Ill. 188.) Here, the Act is capable of being executed. Terms such as “segregation” have a common and recognized meaning.
The Act does not contain any definition of the words “race” or “color”. A similar objection was presented to the court in School Committee of Boston v. Board of Education, (1967) -Mass.-, 227 N.E.2d 729, where the Supreme Judicial Court of Massachusetts considered the constitutionality of a statute providing for the elimination of racial imbalance in public schools. The court cited its holding in School Committee of New Bedford v. Commissioner of Education, (1965)-Mass.-, 208 N.E.2d 814, 818 in dismissing the objection. In that case the court stated: “The city contends that no adequate standards for classifying students as ‘white’ and ‘non-white’ are laid down in the request for a racial census. We recognize the diffi*605culties which may arise in particular cases, particularly in communities with a heterogeneous population. These terms, however, seem to us reasonably susceptible of application by school superintendents and teachers for the present general purposes.” We do not believe that the criteria of race and color can present substantial difficulty to a board in making a racial census. Here, Dr. McCall and the participating school personnel apparently encountered no problems in determining that the Glen Flora school was 98% Caucasian and the Whittier School 85% Negro. Also, as far as we can ascertain from cases dealing with problems of segregated schools, de facto or de jure, school authorities are not experiencing any significant difficulties in making color or race determinations of the type required by the Act.
The defendants also argue that the trial court improperly overruled the school board, which had concluded, based on considerations of traffic hazards, walking distances, finances and classroom capacity, that existing attendance unit boundaries should not be revised.
As stated, the Act provides that "as soon as practicable” a school board shall revise attendance unit boundaries “taking into consideration” the prevention and elimination of segregation. Here, a full hearing was conducted by the trial court at which the parties presented detailed evidence. At its conclusion, the trial court ruled inter alia that the defendants were in violation of the Armstrong Act and directed the alteration of school boundaries as described.
As the defendants state, the trial judge said that under the Act racial imbalance is a paramount consideration in drawing school attendance unit boundaries. However, it is clear from the opinion of the trial judge that he considered and did not disregard other relevant factors in arriving at his decision. The trial judge stated: "Defendants’ evidence concerning traffic, distances of students from school, finances and classroom capacity are not determinative of the issues in the case at bar. In making this statement, the *606Court does not mean to intimate that in a given case these factors could not be the determining factors and would override any factor of racial consideration. In a certain situation the Court feels this could be true. However, in the instant case, the Court is of the opinion that the evidence on these factors was not conclusive, and did not prove that a serious problem, or even one of very large proportions, existed in any of these categories: namely, traffic, distance, finance or classroom capacity.” Later the court observed: “* * * in the case at hand, all of the attendance units involved are contiguous and in a general sense, constitute a neighborhood in the larger sense of the term. This is not an instance where units are separate, nor where any busing or transportation problems are involved.”
The trial court found that no serious problems existed with reference to the so-called traditional considerations and that such considerations were outweighed by the factor of racial imbalance in the attendance units concerned.
We are not prepared, following a review of the record, to declare that the holding of the trial court was manifestly against the weight of the evidence or clearly unreasonable.
Accordingly, the judgment of the circuit court of Lake County is affirmed.
Judgment affirmed.