Complex sentence: Most students have one Alternating Unassigned Time, referred to as AUT, during which students are allowed to go the library and computer labs, seek help from teachers, or, with parental permission, leave campus.
Split into simpler sentences: Most students have one Alternating Unassigned Time, refered to as AUT. During AUT, students are allowed to go the library, computer labs, seek help from teachers, or (with parental premission) leave campus.