School rules should have a purpose, otherwise why do they exist? This question doesn't make sense, as rules by their very nature have a purpose. Actually, come to think of it, practically everything does. So yes, school rules should. Should they have such punitive and ridiculous rules? Absolutely not, of course.
Of course school have a general purpose. School is about teaching young people what to except in life. It will make them aware that life is about choices, and showing respect. School is much better off maintaining their respected rules and not allowing the "inmates' to run the asylum. That would not be very good for the students in the long run.
Some have no purpose at all like no running on campus or no cell phones. Only chumps listen to those rules because they are chumps a n d t h e y a r e f a t a n d a r e s o d u m b