mini metro is out of the question trust me. a book, binder, and a notebook and that thing is 90% full.
i use a citizen for commuting to school. holding a good sized text book, binder, laptop, tools(mini frame pump, rescue tool, tube, tire levers, and 15mm wrench), calculator, a few pens and the bag is pretty full. I definitely would not be able to carry groceries, extra clothes, or shoes.
in a nut shell: if you're only using it for school, go with a citizen. if you need to bring extra items or groceries go with a metropolis.