Lol, the ass size doesn't affect the pussy at all.
Unless you're hittin' it from the back.
I think it's funny how people say some girl is loose when you're still in school. The pussy doesn't get loose after fucking a few guys. It also depends on the size of you're dick. If you got a small one (which I assume you do) most pussy will feel loose to you. I have yet to encounter a 'loose' pussy. But I'm also in high school.