I'm a teacher with an embarassing problem help?

i teach at an all boys school, where i teach english. i am considard a very attractive woman at 26 years of age and have large breasts. I find the boys have very strong erections around me, and some have even had problems covering their bulges with their blazers, there is commentry on my breasts and the boys use their phones to take pictures of me. the problem has arised at a critical point with one boy masturbating behind his bag in class. I have found that i distract them while teaching and it is becoming counterproductive. what should i do?