But teachers in Rhode Island have been accused of overreacting after they banned a pupil from contributing his high school yearbook photograph because it showed him posing as a knight in chainmail, complete with an ancient-looking sword and dagger.

Yearbooks are a rite of passage in the US and school-leavers often pose specially for pictures. Patrick Agin, aged 17, chose his costume because he is a member of the Society for Creative Anachronisms, which researches and recreates medieval history. But it fell foul of Portsmouth high school’s “zero-tolerance” weapons policy.

The American Civil Liberties Union is now suing the school on Patrick’s behalf and a federal court hearing is expected later this year.

The union’s official complaint states that plays at the school have included prop weapons and that the school’s mascot, a Revolution-era patriot, was frequently depicted carrying a rifle.

The teenager’s mother Heidi Farrington said her son did not intend to promote violence: “He sees it just as a theatrical expression of the re-enactment community he’s involved in right now.”