Anyway, it's obvious the reversal of the Bush Admin's abstinence only plan is what caused this immediate drop.
Me thinks you might be slightly missinformed. Yes, there were a couple of "Abstinence only" Federally funded programs, but neither were particularly widespread. One was passed under Clinton and the other under a Democratic House and Senate. They were both wrong and stupid and a waste of govt funds (just over $1 billion between 1996 and 2006), but studies have shown that kids, whether taught Abstinence only or regular sex education have sex at about the same time, about the same amount and use contraceptives at about the same rate.
Some kids/people are idiots, education can only help so much.