Hey Anna,
This happens to lots of people when they move to a new school. I’m sure it’s nothing personal; it’s just that they don’t know you yet. I think you should go and introduce yourself to a bunch of nice looking kids in your class, or at lunch-time, and ask if you can sit with them. It’s probably easier said than done, but once you know a few they will introduce you to the rest.

Good luck!
Lucy x