I graduated from high school almost 3 years ago, and back then, the administration was thinking about putting condom machines in the washrooms, but the parents were staunchly opposed to that, they said that it would just encourage teens to have sex.
Personally, I think it's a good idea. Nothing's going to stop teens from having sex if they really want to, but buying condoms has got to be intimidating (I wouldn't know, I've never bought them, but I know I'd be very embarrassed to do it), so I think it's best to make them available so that teens will actually use them!! If teens want to have sex, they will, but they'll probably be too embarrassed to buy the condoms to do it safely, so they won't bother. If the condoms are readily available and teens won't have to get up the nerve to go to the drugstore to buy them, I think they'll be more inclined to use them. After all, some aunt or cousin or family friend probably isn't going to see you getting condoms from a high school vending machine, but that threat is always there at the store, especially in a small town. I'd be absolutely mortified to have someone see me buying condoms, and where I come from, everyone knows everyone!! Vending machines in schools give a certain level of privacy and anonymity, and I think teens will appreciate that.
That's just my opinion.