Consider this, when it comes to breaking the cycle of poverty a teen is better of being being one grade level behind in reading and avoid pregnancy than reading at grade level and becoming pregnant. Sex education is something that most schools teach and they have various levels of success.

You can also track where a school systems switch to abstinence only education and the rate increases. Now granted it's not supposed to be the most useful thing teenagers get from public schools, but it is a vary important part of their job and we have fairly good data on it as well.