If he hasn't had an attack in awhile it means the hospitalization scared the parents and made the parents and the doctors take his condition seriously. If he now uses his meds regularly you should be fine. Keep puffers at your house and do not be afraid to use the rescue inhaler and call parents. If he develops a cold or other respiratory condition then he should be kept home till you know for sure how he is going to adjust to it. Watch for triggers such as sudden temperature changes ex coming inside/going outside in winter, strenuous exercise, pets.