My classmates are perverted. Help?

Its a new school year and im a freshmen only 13 years old, a boy :)) and at the 2nd week of school, ofcourse i had friends but then the 'popular' dudes wants to talk to me so we hanged out, talked, and suddenly talked about masturbating and who looks hot in our classmate (girl) and i didnt feel really confortable. What should i do??? I want to be popular so will i just scoop down to their level? Will i be like them?? Idk what to do! Help?