PERSONALLY I have a serious personal problem with dealing with children with sickness or diarrhoea so as another parent I would worry an actual bug would be masked by the antibiotic reaction and the school have to have rules that apply to all. Plus as has already been said a child wouldn't want to be at school with potentially running to the toilet all the time.
In our school AB is administered if it has to be taken 4 times a day. Most GPs are able to find one which only needs to be taken 3 times a day unless there are specific reasons to do the 4x/day version.
DD never had issues so I don't know if she would have to tell the teacher. But I know one of her friends had one spell of the 4x/day one and she took it at school. I also know that the girl's head is often in clouds so not sure if she would have thought about it herself.
Our school also has a couple of diabetic children and they keep track of their injections so I would assume they also keep some kind of record to deal with ABs.
If it is an ear infection, the school should give the medicine. For some infections, you can ask your GP to give medicine that will only need to be taken once at school or even not at all in school hours (3 doses that can be done at breakfast, home time and bed time)
If the child gets an upset tummy that might be due to the antibiotics though, they would have to observe the 48 hour rule and stay at home. There's no way you could prove whether the tummy upset was definitely the medication or a contagious bug unless the Dr is happy to vouch for this and tell the school it is due to the medicine.
Even then, a child isn't going to want to be at school all day with diarrhea whatever the cause - it will be uncomfortable and potentially embarrassing.
are children with and being treated for an infection allowed to go back to school (antibiotics) I know with sickness and poops they have to be clear for 48 hours, my dd (5) gets repeated ear infections then ends up with the poops cos of the antibiotics so almost every term is off for at least 5 - 7 days, the school says they can administer antibiotics in school and ask the children to make sure they remind staff they need to take it, my dd can not remember what she did at school or what she had for dinner so I doubt very much she will remember to remind staff she needs medicine and the poops she gets is that then classed as the remain off school 2 days even if its just the medicine.....really confused mum