Tress, if you have a school-age kid, ask them who's the person who's least popular in their class. If they start saying about how "weird" they are, or some other language that justifies being abusive, congratulations,
your kid is a bully. If they're just awkward about somebody, then they're probably just on the sidelines and not
actively bullying, but not stopping it either. If they were standing up against it, you'd already know, since they'd either A) be telling you about it, or B) be the victim of abuse themselves for trying to help, or C)
they are already the victim and
hopefully you already knew that.
In any collection of children (anybody really) over 10 people, the odds of somebody being bullied skyrocket, so it's basically every single class.
Think about it the other way: when have you ever heard about a school that did NOT have this problem? Not claim not to, but actual good contact with the kids? I'm thinking it's basically zero, because "tattling" is still a thing.
I have to stop. This topic brings up emotions that are "not healthy" for me. Rage, etc. Control your little monsters. If you aren't actively asking about it (or them telling you about others) they're probably at the least standing by while it happens, but probably
at least occasionally perpetrating it to make sure they're not the target.