It depends on how the college classifies your son. If he received a 1098-T and the box marked Checked if at least half-time student is checked, then he is considered full-time. He must be considered a full-time student for at least five months of the year.
If he does not get a 1098-T, but the school considers him enrolled in the number of courses to be full-time attendance, and his school is not online-only, then he would be qualified as a full-time student.