here's a way to solve these problems...
go into class just before the exam. maybe go in, drop off your bags so you can save yourself a seat, then go outside & relax off by yourself. don't sit in class before the test & expect everyone else to discuss anything but the test.
after the test, if you don't feel like discussing the test, go off somewhere by yourself or with other people that don't want to discuss it either.
there's no way to control other people's actions, only your reactions to them. i know these things can be annoying, but now that you know how you react, you can change your behavior to make your experience better for yourself.