It’s probably more common now, but this has gone on for decades, at least since the sixties. I think we hear so much about it now because many of the boys we hear about are much younger, not even sixteen yet. Boys that age aren’t as mobile (no driver’s license) as older boys and their parents probably make more effort to keep track of where they are.
I’d bet that quite a bit goes on between teachers and older boys that we never hear about because they are better at keeping quiet, have driver’s licenses and are probably given more freedom by parents.
35 years ago my friend (a girl) was having an affair with her science teacher.