As a society, we are telling kids like these to NOT say no. Sex education programs are saying "You're going to have sex, and there's nothing wrong with having sex when you do want it, so we're going to tell you how to do it." Modern culture teaches kids that sex, especially sex outside of long-term committed relationships, is natural and desirable, and should be wanted and obtained whenever possible.
Simply put, these kids were offered what they were told they should want. We shouldn't be the least bit surprised that they took what was offered.