Student can not concentrate with the hand of the teacher on the cock

my teacher always asks me to stay together hours after the end of the lesson. I don’t know, but always insists on the fact that I need an extra help for my classes. Today told me that my problem was concentration, but she had the solution. He practiced an exercise that would help me to eliminate distractions. He asked me to solve some math exercises, and then I put the hand on the cock. He told me, assuring that it was part of the exercise, I pulled out the cock from his pants and started to jerk off. It was impossible for me to concentrate as well, but its intensity increased because then used to the boobs and finally the mouth. I have not been able to do anything until I ejaculated, but I failed in the exercise.