Next year, I’ll be attending a strict private school I was really excited an all UNTIL….?

I pulled a prank on someone with a friend (she won’t be going to the same school as me next year, though). We editted the color and banner of someone’s website and added a guestbook and chatroom. We signed with a nickname (it was NOT someone we knew, it was a humorous name). Now mind you, this website was a not-so-famous band’s website (I was the original designer for it, but they soon fired me), and they had changed their name, so naturally you would only expect for them to MAKE A NEW ONE, since they supposedly weren’t even using the one we editted anyway. We didn’t intend for it to get so out of control, an we deeply regret what we did. Now, one of the band members will be attending my school. He says he’s geting revenge on me. I know they dont tolerate such behavior, so if he gets in trouble, he’ll say everything I did to his website (and maybe exaggerate). I know the school does not allo use of underage drug or alcohol abuse, but would this also be a reason for expulsion?