Complex sentence: Abstinence-only sex education is a form of sex education that teaches abstinence from sexual activity outside of marriage, and often excludes other types of sexual and reproductive health education, such as birth control, contraceptives and safe sex.
Split into simpler sentences: Abstinence-only sex education is a form of sex education that teaches not having sex outside of marriage. It often excludes other types of sexual and reproductive health education, such as birth control and safe sex.