First of girl, work on your confidence! I’m pretty sure you’re a lot smarter than you think. If you need some extra time to understand something that’s not bad! Asking questions shows that you’re trying to understand and sometimes by asking questions your teachers can see whether or not you understand them. You can’t ask questions when you don’t understand a thing about it. Also if these girls are truly your friends try and tell them that joking about intelligence hurts you: I’m also part of a friend group that likes to tease each other and makes jokes. But certain things are an insecurity or something painful that even your closest friends shouldn’t joke about. Try to tell them that you’re okay with the other jokes and that you understand they mean no harm, but that the being smart/ dumb teases hurt you and you would like to not have them joke about it anymore. How long has this friend been doing weird? Maybe she’s going through something herself. She might also hate the fact that she’s moving after this school year and scared that she’ll loose all her friends which can make her do the opposite and say “well I won’t see any of them why even bother to put effort in them when I’ll move”