Get ready for a quiz on racial fairness: what it is and how to achieve it.

The facts are these: In 1974, the Boston School Committee was found guilty of racial discrimination in the hiring and assignment of teachers. U.S. District Court Judge W. Arthur Garrity ordered the committee to correct the bias by hiring one black teacher for every white teacher hired until the overall proportion of black teachers reached 20 percent--roughly the percentage of blacks in Boston.

It worked. By last year, slightly over 19 percent of Boston's teachers were black-- up from 5.4 percent when the quota plan was introduced.

Question: Was the plan fair?

The Boston school system recently ran into financial difficulties, making it necessary to lay off a number of teachers.

Question: How should the layoffs be accomplished?

The method specified in the teachers' union contract is by seniority. But because so many of the black teachers were recent hires, layoffs based only on seniority would reduce the proportion of black teachers from 19 percent to only 8 percent, effectively wiping out the affirmative-action gains of the past eight years.

In recent years, courts have avoided the seniority/affirmative-action dilemma by awarding retroactive seniority to individuals found to have been earlier victims of discrimination. But in the present case, there is no contention that the recently hired black teachers were previously discriminated against.

Nevertheless, the school committee asked and was granted court permission to ignore the seniority clause of the teachers' contract. The upshot is that only white teachers--some with 10 or 12 years' service--have been laid off, while a dozen new black teachers have been hired.

Question: Is this fair?

It has sometimes been proposed that, in order to salvage recent affirmative-action gains in the face of work-force reductions, layoffs should be allocated on a proportional basis. That is, if the staff is 12 percent black, 12 percent of those laid off should be black. But Boston never reached the court-mandated 20 percent, and until it does black teachers are immune to budget-induced layoffs.

Another complication. According to Albert Shanker, national president of the American Federation of Teachers, "the Boston School Committee has announced 595 additional layoffs (in addition to the 550 already furloughed), again all white, some (of whom) have been teaching for 18 years. On the very day the layoff notices went out, the school board . . . announced a recruitment drive for new black teachers."

If blacks are let go on a last-hired, first- fired basis, then you are back to the discriminatory situation that led to the special hiring mandate in the first place. If blacks are held immune to furlough, then innocent white teachers are punished for the school committee's discrimination.

Question: Which is the least unfair?

The answer is important, not just for Boston but in other cities -- Springfield, Ill., Buffalo and Kalamazoo among them --where the rival requirements of seniority and affirmative-action have resulted in whites-first layoffs.

There are other, equally difficult questions. For instance, one of the reasons given for the Boston plan was that black students are entitled to a fair proportion of black teachers, as role models. But as Shanker asks, are they not also entitled to experienced teachers?

Finally, there is the fundamental philosophical question. Granted that without some outside leverage, many employers-- arguably including the Boston School Committee--would continue to favor whites, what should be the guiding principle? Should we recognize the predisposition of whites to favor whites and build in protections for blacks as blacks? Or should we buy Shanker's notion that America stands for "the opportunity of each individual to achieve his or her potential without regard to ancestry"?

The U.S. Supreme Court has agreed to hear the appeal of the Boston teachers' union on this vexing question. What should its answer be?