Are there places in the cafeteria or anything, gym bleachers? I would see if I could find a geometry tutor (I had to retake geometry :-) either from school or out of school, maybe ask that teacher for extra help/go sit there in the mornings for a bit until time for whatever class in whatever room? It might not be so hard sitting in a class trying to understand that class' subject while the teacher was there? Getting to know the teacher a little bit could help your grade; if they get to know you you won't flunk Been there, done that.