"My biggest problem with Harry Potter is that I went to an English public school and hated it," he says. (By "public school," the English mean what Americans mean by private school.) "I would have rather lived under the stairs." When he was 17, Gaiman wrote his own novel about English schools. "At the end, all the dead teachers came back to life--there was sort of this plague of zombies ripping the thing apart--and our decapitated hero had his eyes pecked out by the school peacock. That for me was trying to write a version of my own public school experience that was nicer and more fun."
(Thanks to Sarah for the link.)