From IRS Publication 501 (page 12):
"Student defined. To qualify as a student, your
child must be, during some part of each of any 5
calendar months of the year:
1. A full-time student at a school that has a
regular teaching staff and course of study,
and a regularly enrolled student body at
the school; or
2. A student taking a full-time, on-farm training course given by a school described in
(1), or by a state, county, or local government agency.
The 5 calendar months don't have to be consecutive.
Full-time student. A full-time student is a
student who is enrolled for the number of hours
or courses the school considers to be full-time
attendance"
