My Friends Keep Turning On Me?

Two out of three of my closest friends, have turned on me. The third one has been my best friend for four years. She is firmly with me on this one. All three of them are going to the same high school next year, but I am not. At first, the two friends that have been talking about me, have put me down for it. They said that they were hurt that I would choose a high school over our friendship, after I decided to accept the schools offer. They showed some support when I was making my decision, but keep bothering me about it when the topic isn't relevant. Today, I learned that one of the two friends who doesn't really like me, called me a backstabber and a betrayer, for going to someone else's party days after declining the offer to go to her party. I did not go to that party; I wasn't even aware there was a party. She wouldn't answer my calls when I tried to contact her, so I messaged her on facebook. It's been bugging me that she and the other girl have the nerve to tell me that I'm a bad friend for trying to make new friends. A couple of years ago, I drifted away from my first best friend. I talked and hung out with her more this year, and my current best friend supported me, because me and my old best friend ended on bad terms. The other two, decided to call me out as trying to ditch them. I'm really annoyed right now. They wont give me the opportunity to confront them. I know that they have a right to feel like this, but I'm afraid that I will always be criticized for hanging out with other people. I got invited to the pool by some of my other friends, and I'm afraid that going will cause drama and damage to our friendship. Can you help me? What do I do?