School for little monsters - Michelle Robinson

A little boy and a young monster accidentally switch schools on their
first day, with hilarious results. At the School for Nice Boys
and Girls, the monster is surprised to learn he must sit still,
be quiet, and wait in line. Meanwhile, at Monster School, the bewildered
boy finds himself launching a custard pie attack, counting
bogies and sharing nasty smells. The child and the monster play
by each other's rules, at first bewildered, soon horrified - and
eventually getting into the swing of things.
This madcap tale is perfect for little monsters everywhere!