Because kids are going to do it weather their parents want them to or not, and some dumb ass parent restricting their kids access to birth control is just going to end up with a grand-baby, then they'll blame the school for not "doing their job" whatever they think that "job" is.
The reason I say "only condoms" though, is because if a school can't give out pain meds without permission (at least my school couldn't... Which was a pain for me because I suffered chronic stress-headaches) then they shouldn't be able to give out something as serious as the pill. The school should TALK about the pill though, and perhaps have somewhere like a local clinic where they can refer girls to talk to a doctor about it if they're serious about the pill.
Okay, I'm not saying that a school should endorse sex in any way, but we all know that teens (I believe you are talking about High School) will have sex. There just isn't a way to stop them the urges are to strong. But, by schools providing them with Birth Control (with parental permission) then we can probably prevent some of the unwanted pregnancy's that occur.
No birth rate must not decreased because it kills the sentiment of a parent .Every women wants beliefs that when she become a mother for a child then she is a complete women.Decreasing the birth rates is equal to the killing of a child and sentiments of a mother . Think over this!!!!!!!!!