After reaching Level 30, the Headmaster starts a conversation with you again.
The Headmaster tells you that you need to take the After School Special Training. You should go to class and meet your teacher. Special Training, Class, and Teacher are the Resistance passwords! Go to the Resistance Underground Base and meet Brighton.
You have a new mission as a Resistance member. It's a tough mission, specially assigned to you... You cannot refuse it, nor do you want to.