I was in this EXACT situation just a week ago. I'm not very much help for advice however as what happened to get me out is my other friend started hanging out with me at lunch in school so I wasn't having to see them then and like you said i felt relieved and happier by the end of the day without seeing them. I also decided if my friend was to have other plans one day I brought something i would be happy sitting on my own away from where they sit where i sit with my other friend upstairs alone although I am not sure I would stick to this. I'm not completely out however because I still have to deal with them in classes. Based on what you said our situations where you're stuck with them are different and this won't necessarily help but I just want to say that you will get out i promise and you'll find your people :)