The Sun Journal says the teen was suspended in accordance with Lewiston High School policy after the toy fell out of his backpack. The student wasn't identified.
School Superintendent Bill Webster tells the newspaper that the suspension could be reduced and that administrators "will work to balance the discipline with the facts of the case."
He also says that water pistols, even ones that don't look like guns, can be disruptive.
Across the country, schools are grappling with the issue of how to handle weapons, both real and fake. Some students have been suspended simply for pointing their fingers in the shape of a gun.