When a school of choice has space available and accepts a student from outside its attendance zone, HISD requires that the parents agree to keep the student at the chosen school for the entire school year. Parents may also apply to a school other than the "zoned" campus for other types of transfers, such as impassable geographic barriers, space-available, out-of-district, adequate yearly progress (AYP), and public education grant (PEG). Students are only allowed one transfer of any type per school year. Should a student choose to leave the school to which he or she has transferred, that student may only return to the zoned campus.