It may not be easy to distinguish between a fetish and a real need to wear diapers. I have seen some of Will’s posts on this site and he says that he does not like having to wear diapers at night or having accidents during the day. I would guess the question is whether he really has daytime bladder control problems or whether he just waits too long to make it to the bathroom. It’s not that unusual for someone with problems to want to use protection just to avoid the embarrassment of a public accident, and if he really needs the protection then it would be reasonable for him to wear them to school. You probably know whether he has physical problems with bladder control, so you should be able to tell if he needs the protection or not. Wearing diapers around the house where bathrooms are readily available may be another issue, but I have read accounts of adults that struggled with poor bladder control and fear of accidents for years before finally giving in to wearing diapers full time. Even though they could make it to the bathroom most of the time, the stress of worrying about when and where the next accident would happen was too much to deal with. A person may “like” wearing diapers because it makes them feel more secure. A frank discussion with him about whether he feels that he really needs the diapers or whether he just likes to wear them might help resolve the question. What you do then is something you and Will have to decide.