I am a nurse. The 30 min rule is what is used in the hospital, and usually applies to those drugs that are on a timed schedule several times a day, like every 4 hours for example. It is there to ensure a medication does not get given twice in one hour for example.
I now work in the school system. If I were you I would have the doctor change the order to once daily. That way it gets administrated once period. Is there any way this could even be given at home? My son takes a lot of medications but we give them all at home that way we don’t have to deal with school staff. Good luck.