Easy, repeat after me... "Would you like an apple pie with that?" Or "would you like to upsize your combo for $50 cents more?" Practice that in a mirror until it scares you enough to pick up your pencil and get back to those books. It sucks but then again, so does poverty. I speak from experience.
Ah, homework. The worst type of thing the teachers can lay on you, except the talk. I feel your pain. Don't do it, and if you have a rep with the teachers like I do, which just happens to be teachers pet, then sweetly explain to them that you were busy, throw in some excuses, say it'll be done tomorrow, and you're home free. I do it all the time. Trust me. It works if you have a rep like mine. :)