What would you do in this situation?

At school we have this project we have to do and we are in pairs. (We did not get to pick our partners) Okay this guy i'm with isn't doing none of the work! I'm doing all the work while he's flirting and listening to music and acting retarded. I don't know if i should tell...but then id b a tattle tale...or should i just let him continue because he said he would work tomorrow (but i don't believe him.) What should i do and what would you do???