So i like a few different "styles" of Tetras. If I had a couple of different styles in a 55 gallon tank would they school together or stay in separate schools ?.
Yes, depending on how similar they look, like Cardinals and Neons will school together, whereas Neons and Lemon Tetras will not. You might not want to go more than 2 kinds of schooling mid-level species for your tank, too many would just look like a mess IMO.
I have a single rummynose tetra in QT right now and he happily swims with the half a dozen neon's that are also in QT. Pretty funny to watch him swimming around in there, he will probably be sad when I move him in with the other rummys that I already have. Even more so since they are double his size and the neon's are about the same size.
neons and cardinals, yes, but beyond that schooling with other species is relatively uncommon. tetras of another species will only usually school with another if they are the only specimen of the species and the other group is large enough to be a school.