Restricting Wireless Access on Campus?

Diety_in_A_Minor asks: "How would one set up a wireless network on a campus such that restrictions can occur by classroom? My back of the napkin solution would be to relate MAC addresses to class schedules, and have the DHCP server allow access to student-registered MAC addresses only during specific times. Although possible, this solution requires tremendous maintenance. What other solutions are there? One class in a building will require restrictions, while both classrooms adjacent to it need open access."