WASHINGTON, Dec. 4 — By the time the Supreme Court finished hearing arguments on Monday on the student-assignment plans that two urban school systems use to maintain racial integration, the only question was how far the court would go in ruling such plans unconstitutional. [Snip] Before the arguments on Monday, the challenge for the school board lawyers defending the plans, along with their allies in the civil rights community, had appeared to be to persuade the justices that the appropriate analogy was not to affirmative action, a freighted subject for the court in which benefits are bestowed on one group...