Helene Patterson and her boyfriend, Joe Temperino, both 17, display a condom they obtained from John Dewey High School, one of two schools to inaugurate New York City's controversial condomdistribution plan. The city board of education decided last year to let high schools hand out condoms to students without the knowledge of their parents. Since then, school officials in Philadelphia, San Francisco, Seattle, and Falmouth and Martha's Vineyard, Mass., have also agreed to make condoms more readily available to students in an effort to reduce the spread of AIDS. Many other districts are considering similar approaches. About 20 schoolbased clinics nationwide have been distributing contraceptives to students for some time. What is different about the new plans is that most would allow students to get condoms from a nurse, teacher, or vending machine on school grounds.