Well, if you just let it fester, it will only get worse. I read your journal, just didn't comment. I understand you won't feel safe, I certainly wouldn't. If you press them (the police) to do something, tell them exactly what some of the people looked like or even offer a vague description, then something will be done soon enough. Tell your parents, your principal, your teachers, tell everyone who can do something about it.
And if those "friends" stood and watched when you got dragged off, I think it's time you ask them about that.