The post I linked to this morning reminded me of an incident from my youth. I'm putting it here because I think it's a good example of how these sorts of things should be handled.
When I was in fifth or sixth grade - so, eleven or twelve years old - I got it into my head that it would fun, or funny, or... well, or something to "pop" a girl's bra. If you're unfamiliar with the term, it basically means pulling the back of the bra out and letting it snap back into place, rather like popping someone with a rubber band. I cannot for the life of me imagine where I got this idea - other boys talking about it, maybe? - or why I thought I should try it.
But I snuck up behind Olivia (I think), and I popped her bra, and I ran off before she had a chance to even process what had just happened, let alone react.
And about five minutes later, one of the teachers came up with Olivia, and sat me down, and asked me why I'd done that. I didn't have an answer, and I don't to this day. I can tell you that it wasn't because I "liked" Olivia - or disliked her, for that matter. This was at that stage where the girls are frequently taller than the boys, and she had developed a bit earlier (and more visibly) than most; that probably had something to do with the "why her" part of "why", and I'm sure I didn't do her emotional well-being any favors by popping her bra.
But the teacher explained that that sort of thing wasn't acceptable, that it had hurt Olivia, and that I needed to apologize to her right now and never do it again. And I apologized to Olivia, and I never did it again.
Thinking about it later (I tend to process things slowly, and after the fact), I was surprised that I hadn't even considered that it would hurt. In the moment, it seemed funny and harmless for me, and it never occurred to me that it might not seem funny and harmless to her. It should have, but it didn't.
So that's the story. It was far from my finest moment, but I think I did learn from it. And, Olivia? I'm still sorry about that.