Providing first aid or breaking up a fight is totally different from dealing with repeated soiling by the same children.
But lets use your examples there as a point of note, Use this following example:
If while the teacher is cleaning my child, your child had a fit or was getting hit by another pupil. Would you think that acceptable?
Children, boys especially will start to get up to mischief when the teacher is out of the class. They are at higher risk of eg falling off a desk and injuring themselves, because lets face it us boys are a bit stupid when young.
You then have the added pressure of the teacher settling that class back down before lessons can resume. So that one soiled child could well easily reduce learning time by an hour.