If you're interested in doing some screen printing with your students, here are two great tutorials, both of which photodocument the process.

Posters: This tutorial is an exhaustively detailed explanation about how to print posters from start to finish. Warning: While there's nothing particularly offensive on this page, the name of his website probably could be a tad inappropriate for schools. So if you're going to show this to the class, screen it for yourself first (get it? screen it for yourself...? Ah nevermind.) There's also a picture of a beer bottle, in case you're worried about your students discovering the existence of alcohol...

T-Shirts: This livejournal user provides a great tutorial on how to silk-screen inexpensively.