The impact of three variations of a family life education (FLE) program for 172 inner-city, junior-high-level students was investigated. Variations in exposure time, instructional methods, and teacher quality led to the classification of each intervention on a general intensity dimension. Separate pretest-posttest nonequivalent comparison group designs were utilized to assess program impact along seven knowledge and attitudinal dimensions. Survey results revealed that, in comparison to no-treatment groups, the more intensive the program (a) the greater the gains in knowledge about reproductive physiology, contraception, and the consequences of teen pregnancy and parenthood (especially among experimental group females); and (b) the more birth control methods participants became familiar with over time. Changes in personal acceptance of premarital intercourse and perceived responsibility for contraception were observed only in the study examining the most intensive treatment. The results of the evaluations point to the combined importance of instructional methods, teacher quality, and in-class exposure time for producing change in young adolescents' knowledge of and attitudes toward sexuality. Further potential for the impact of school-based sex education programs on knowledge and attitudes is discussed within the broader context of the young adolescent's social environment.