What classes do you need to have before going to college for vet tech?

If you are going for a 2-year A.S. in Veterinary Technology then you don't need any classes before starting. You can take all of your general education classes while taking your vet tech classes. If you are talking about a 4-year B.S. in Veterinary Technology then you should check with the program and the university for their requirements. Typically, most universities require college Biology, Chemistry, Organic Chemistry, Physics, and Calculus as prerequisites before starting any B.S. programs.