Note that I said guess. It isn't possible to know without a site survey and a sense of your application and throughput requirements. You need a survey to identify RF obstacles like steel posts and plumbing and to measure actual signal loss due to your walls and first-floor ceiling. According to Planet3 Wireless, dry wall cuts effective range in half, but a solid-core wall (or ceiling) drops strength to 15%. If your users need higher sustained throughput, you could deploy 802.11a or 802.11g instead of 802.11b. Another consideration: If one AP is down, do you need distant students to be able to use the other AP at a lower rate?
You could hire a local network integrator to perform a site survey, refine your requirements and install the AP(s) you need. Or you could conduct a site survey yourself: buy one AP and card, put the AP where you think you might want it, and use a laptop with monitoring software that comes with the card or NetStumbler to take some measurements. Map out where link speed drops from 11 to 5.5 to 2 to 1 Mbps by walking very slowly away from the AP, standing in the corners and center of each room, etc. Relocate the AP if necessary to eliminate important RF deadspots. Most APs can support 20 associations, but your real limitation probably will not be connection limit. Throughput requirements will dictate what kind of link speed you need to deliver per user and therefore how many APs you will need.
As for hardware, you could buy a broadband router/firewall with integrated DSL modem, hanging APs off the router's Ethernet. Or you could buy a basic DSL modem from your telco and a separate SOHO/wireless firewall, hanging APs off the firewall. Why bother with a separate firewall? Because some firewalls provide bandwidth management features that let you limit per-station or per-group usage - for examples, see the NetScreen-5XT, WatchGuard V60L, Bluesocket WG-1000 SOE and ReefEdge CS-50. When selecting APs, give some thought to security - if you need to keep users from breaking into and reconfiguring your APs, steer clear of entry-level APs that lack security features like configurable admin logins, port numbers and interfaces and support for secure management protocols.
This was first published in April 2003