Mandie Watkins said her son, Alex, a second-grader at Mary Blair Elementary School in Loveland, was suspended from school when he threw the imaginary grenade -- which was not represented by a real, physical object -- into a box while playing a game he called "rescue the world," KDVR-TV, Denver, reported Wednesday.
"I pretended the box, there's something shaking in it, and I go 'pshhh,'" Alex said. "So nothing can get out and destroy the world."
Administrators said the game violated one of the school's "absolutes" against any weapons, real or imaginary.
"Honestly I don't think the rule is very realistic for kids this age," Watkins said. "I think that when a child is trying to save the world, I don't think he should be punished for it."