Huh?

I'm working with jake on his teachers names. He knows the head teacher is Ms Jennifer but has two aids. I asked if he knows them yet. He responded in the affirmative. I asked, "Then which one is Ms Mas?" to which he replied, "Ummm. The last one." I was sort of expecting him to tell me what she looked like so I'm not sure what to mar of that answer. Maybe she is last in line everytime they leave the class or something.