20 CFR 216.75: When a child is a full-time student during a period of non-attendance.

A student who has been in full-time attendance at an elementary or secondary school is considered a full-time student during a period of non-attendance (include part-time attendance) if:

(a) The period of non-attendance is 4 consecutive months or less;

(b) The student shows to the satisfaction of the Board that he or she intends to return, or the student does return, to full-time attendance at the end of the period; and

(c) The student has not been expelled or suspended from the school.