I didn't go to a "religious school," but I did attend public high school in Texas.

Our health teacher was a coach, and he went over sex education. One day he said that condoms don't eliminate risk from STDs, they just reduce it by about half. Even wearing two condoms doesn't really eliminate the risk, it just reduces it by another 50%, so you've still got a 25% chance of getting something.

I was a pretty naïve kid, but even I knew that was fucking stupid.