you mentioned two things that might. First, Windows will have a fixed number of PCs that can be accessed at one time unless you run some server edition. Secondly, you mentioned files but also a learning module. Do you mean you need to run software remotely? What I've seen done with some applications in school environments is to use client software on all PCs and store a database on a server device. I set that relationship up in a school myself using Windows XP embedded on a NAS. That one came with a 25 client limit. Setting up the wireless will be as easy as putting up a WiFi router with nothing connected to the WAN port and configuring all devices that pass through it. You'll need to connect via wire to the router at first so you can set up security, IP addressing, etc.
Tell more about whether the laptops will just need to access files from a share or need to actually access software. Tell how many simultaneous connections will be needed. Win XP Pro only allows 10 but I believe Win 7 Ultimate allows 20. I'm not sure about Win 7 Pro.
I have been tasked with facilitating the set-up of a wireless network within a classroom that will access files from a teacher computer (no internet is available to us whatsoever). The main objective will be to access a Learning Management System called Moodle with a total of 30 laptops. What would be the easiest and cheapest way to accomplish this? I will purchase a 'mobile computing lab' (30 laptops in a movable cabinet), but have no idea how to approach the networking issue. Thanks in advance.