A classic of 'preAcademia' is
A Clerk of Oxford and His Adventures in the Barons' War by Evelyn Everett-Green available from Gutenberg.
A completely different kind of school based books are the MacDonald Hall series by Gordon Korman, set in a Canadian boys boarding school: (
This can't be happening at MacDonald Hall, Beware of the Fish, The Zucchini Warriors, The War with Mr. Wizzle...). They are written at the middle school level but are very very funny.