If anyone can just saunter in whenever they feel like it, then the scheduling and
therefor the rhythm of the class is broken. Being sent home a few times will send a
clear message to the student. Of course the are exceptions, however I have
found that the majority of the time it is just poor planning or an non serious
mindset of the student.
Sent home? I don't think that I'd feel too comfortable practicing at a dojo where they treated me like an eight year old.