My ex-friends are being rude to my new বন্ধু and I

I used to be বন্ধু with two girls named Kathy and Julia. Kathy was my best friend, but Julia is just a jerk. She would always try to get me to stop being বন্ধু with Kathy--hit me, tell me Kathy didn't like me, tell Kathy that I didn't like her, calling me rude things, etc. But then Kathy started being rude to me, too, and ignoring me. So I decided to stop being their friends. I got a new বৃত্ত of friends, and my current best friend Tessa. But now both of them are being horrible to us, Julia especially. She finally got what she wanted; for me to stop being বন্ধু with Kathy, but now she still wants to mess with us?
I'm completely at a loss here. It feels like my fault that they're mean to us, and I don't want Tessa to stop being my friend because of it. We've told teachers and parents and everyone we could about it, but it only seems to make it worse. What should I do?