It does go without saying, that's why it should be the first and most emphasized option taught to teenagers in sex education. I'm not saying abstinence only sex ed is the only or even main reason for the drop. What I'm saying is the argument that "you can't stop kids from having sex, so we should teach them safe sex first" simply isn't true - the trend is clearly reversible, so it's not unrealistic to think it can make an impact. And I'm not saying abstinence only will bring the number down to zero - that's clearly not possible but the idea that it should be abandoned or de-emphasized in favor of contraceptive teaching/training is dumb. It should be abstinence first, it's clearly the smartest option for young people, especially young poor people.
People who lack the resources, maturity and responsibility to deal with the consequences of certain behaviors should be discourage from engaging in those behaviors. The Brookings study should be taught in conjunction with sex education.
https://www.brookings.edu/opinions/...teens-should-follow-to-join-the-middle-class/
And to preempt any claims about conservative ideology entering the study, Brookings is a self-described liberal-leaning think tank. Sorry if pointing that out offends you.