honestly, you have several different approaches to labs these days: Apple, PC (from an established Tier 1 vendor like Dell, HP, Lenovo, etc.), or do-it-yourself. If your school district already has an open agreement with one of those entities, they should be able to provide discounted hardware costs.
in terms of software, a good exposure to Linux (or OpenSystems) is vital. I’d hazard a guess and say that pretty much anyone knows XP/Vista and Mac OS X. To that end, it may be worth using something like VMWare Server or Workstation to allow someone to play with Linux in a more contained environment.
just my thoughts for you.