Emboldened by the political right's growing influence on public policy, opponents of school activities aimed at educating students about homosexuality or promoting acceptance of gays and lesbians are mounting challenges to such programs, at individual schools, at statehouses and in Congress. Chief among the targets are sex education programs that include discussions of homosexuality, and after-school clubs that bring gay and straight students together, two initiatives that gained assent in numerous schools over the last decade. In many cases, the opponents have been successful. In Montgomery County, Md., for example, parents went to court to block a health education course...