CCNA is the begging level of Cisco cert. Its a book test, and the cisco academy program is really good for preparing you for it, and for learning networking stuff in general. I don't know how your teacher would teach it, but we took it at a crazy pace, we went through a whole semester in like 3 weeks. It was way too much information for that amount of time, but some of it seemed to stick OK. Just make sure your class splurges for a nice lab, like 5 routers with some switches and hubs, and like 10-20 workstations. Actually working with the stuff is better than doing some dumb simulation.
Go for it though, its not like it can hurt you. After that, its CCNP, i think you take a series of tests for that. After that is CCIE, thats a two day exam, they say you should have a few years experience before you go for that one, though.