I am not sure what the best solution is for 60,000 students. It seems to me that if 60,000 students were going to self-register, that you would want the default role to be "student" and that you would not want to verify each student account and set their role. This might take you 1000 hours just to verify them.
I never deal with this many, so I am not the best person to help you. However, you might be able to upload a list of your teachers, setting their role as "teacher," and then let the students default to "student."