Sixties social ferment, Seventies torment. The crucible year of the title is 1963--when Kennedy is assassinated; the free-form Humanities seminar at Oakridge (N.J.) High puts on Arthur Miller's Crucible; and 16-year-old Elizabeth Newcomb, ""changed"" by a social-service summer in Dominica, sees the play's conflicts come to life. Playing the lead roles with her, onstage and off, are new love Paul Brandini, musically-inclined son of a business-minded father; new, outspoken best friend Mollie; and Mollie's boyfriend Jay--whose parents are close to the Brandinis, while he hangs out with Mollie's disreputable older brothers. The unwitting catalyst is non-conformist teacher Ian Cartwright, who's warned the kids against that ""moment of truth. . . when we look into the void of chaos and see our naked self."" In the Soap-operatics that follow this high-level patter, Paul sees his father making. out with Jay's mother, Ian is accused of corrupting not only the kids' minds but their morals, and Paul's sexual orientation, in particular, is questioned--whereupon Elizabeth feels called upon to demonstrate otherwise, and then draws back. Bisexuality comes off looking pretty bad in this book (that, at least, is 1963 for you), notwithstanding the final plea for ""more understanding"" for everyone--including the uptight principal who brought down Ian. But to take this as seriously as it takes itself would be ridiculous too.