Their reason? They were impersonating Captain Underpants, a US children's book icon. "There's a dress code which prohibits students from wearing anything that causes a distraction from education, or be deemed inappropriate," said Terry Gilberto, spokesman for Long Beach high school, whose former pupils include Hollywood comedian Billy Crystal. Mr Gilberto reported: "Principal Nicholas Restivo said, 'You guys look too much like you're trying to be naked - other students are making comments'."
Captain Underpants is a tubby, bald cartoon character - naked but for a pair of large white skivvies and flowing red cape - who tangles with scourges like the Incredibly Naughty Cafeteria Ladies from Outer Space and arch-nemesis, Professor Poopypants.
The students spurned offers of school clothing to wear underneath the underpants and walked out of school for the day. But disciplinary action was confined to detention for one of them for cutting class to do a TV interview.