Well, since it's for education, and you won't be doing a lot of (if any at all) 3d gaming, then don't worry to much about a graphics card. However, don't go super cheap on graphics either....middle low end would be good (you know, maybe 3 or 4 on a scale of 1-10).
Most of the education laptops that I looked at had the core 2 duo in them, which are pretty dang fast! I'd go with a full 1 gb of ram (2 if you'll be running vista). This will help to keep it fast for a few years and also leave enough ram for the shared (integrated or onboard) graphics.
Speaking with Vista, get with your IT people and see if they're up to snuff on the security and whatnot for Vista. It's new, so it's new to the IT people too, so you're IT folks might prefer XP (or XP pro) due to the fact that they know that OS and can already configure it.
The wireless (wi-fi) should either come standard or be an option that you can upgrade to. Check around, and get the best price (duh!). Also, don't be afraid to find a comparable model between (for example) Dell and HP and call one and say "well, Dell has this same thing for $xx dollars less (hey, it works for the regular customers right!)
Tablet PC's......I have no clue, sorry!
However, I can say that I'd stay away from them (except for maybe the teacher) due to the fact that I'd be afraid that the students would be to rough on them and they'd stop working (I'm sure that "abuse" isn't covered under warranty). Just MHO
Hope this helps!