This is why abstinence only sex ed will never work. You will never, under any circumstances, stop teens from having sex, and when they aren't taught how to protect themselves when they do have sex, you end up with teen pregnancies, STDs, and a high abortion rate.
Teaching abstinence should absolutely be a part of sex ed, but teens need to be taught how to protect themselves if they do choose to have sex.
Abstinence only sex ed is like communism. It only works on paper, because it doesn't account for human nature.