$50 for 1 gb of ram and a windows version upgrade is probably worth it, though since i'm not sure what you'll be using it for in school, you may not notice the difference. You'll only notice a difference when gaming, or working with RAM hungry applications like photo/video editing software.
How about this:
If you're an engineering/art/architecture student, go for the 4gb ram version (tho if you're an art student, why aren't you getting a mac? :P).
If you have a serious interest in photography or have (or will get one in the future) a DSLR camera, get the 4gb version.
If neither applies, then the 3gb will probably be enough for you.