Complex sentence: Abstinence education teaches children and adolescents to abstain from sexual activity, and that this is the only certain method of avoiding pregnancy and sexually transmitted infections (STIs), and that abstinence until marriage is a standard by which to live.
Split into simpler sentences: Abstinence education teaches children and adolescents to abstain from sexual activity, and that this is the only certain method of avoiding pregnancy and sexually transmitted infections (STIs). Programs also teach teach that abstinence until marriage is a standard by which to live.