That is out of control.
I have to admit that my high school also had a hazing day, although I admit it was nothing close to this. It was called "Freshman Trash Day" and it always took place the day before winter break. Mostly it consisted of juniors and seniors taping freshmen to trash cans or lockers, or marking their faces up with permanent markers (mustaches, "Seniors '03," "freshmen suck," that sort of thing). I hear that in the past it was much more violent -- taping freshmen into trash cans and then rolling them down the stairs, beating the freshmen up if they walked through certain hallways, things like that. The school has really cracked down on it, although they haven't been able to get rid of it entirely.
In recent years it's become almost a status thing to get trashed, because mostly the upperclassmen will only trash the freshmen they know, and then only mildly, as a joke, and the freshmen are all excited because it's like a badge that says "I'm friends with a senior!"
I'm sure we weren't the only high school to have some sort of hazing-like tradition like that.
In this (much more disturbing) case, though, couldn't they make the case that these junior girls were going along willingly? I mean, if it's an event that takes place off school property and without the school's consent, it's not like the juniors HAD to be there. They went because they wanted to, and they knew what would happen to them if they did.