The reason they do this is for legal reasons and because if you are allergic to things like pain relievers, you could have serious reactions in some cases. also because they don't have direct permission of the parent in that moment. Also most of the time you are supposed to bring in your own medication, like write ur name on the bottle and put the bottle in a baggie
Me and my friends all sit in the front row and get called teachers' pets because we act good in class and get good grades and all my other classmates take advantage of the substitutes.