The WS2000 is EoL and as such I wouldn't recommend it. The replacement for the WS2000 is the RFS4000 which supports 6 APs (802.11n capable).
You probably need to-do a site survey to really understand the RF behaviors at the physical location. I've found (in volunteer work I've done) that school buildings are usually built with some very thick concrete (steel reinforced) walls which really limits the 2.4Ghz and 5Ghz RF signal. I haven't yet had the opportunity to test an 802.11n design in a similar environment.
I would probably recommend an RFS6000 with
x number of AP650s (thin access port supporting dual radios with 802.11a/b/g/n configurations). You'll need a decent wired network to interconnect the APs and the RFS6000 with PoE capability if you wish to power the Access Port.
The issue with iPads, iPods or iPhones is that they all max out their transmission power at 10mW. A laptop by comparison will usually put out between ~ 50 - 100mW. If you can't do a survey I would probably start with the worst case scenario which has you putting a single AP in every classroom. If costs are a concern you could look at utilizing the AP6511 which is a single radio Access Port and can easily connect to an existing wall jack.
http://www.youtube.com/watch?v=fnnuQXm1_DMGood Luck!