The 15-year-old suspended for 10 days was disciplined after the toy gun fell out of his backpack at Lewiston High School. His name was not made public.
Under the rules of the game, participants try to squirt an assigned target, often in public.
Detective Sgt. Joe Bradeen tells the Sun Journal that Lewiston residents have been calling police lately to report strange vehicles and people walking through their neighborhoods, often at odd hours. He says some squirt guns look like real weapons, which could lead to a dangerous situation.
School Superintendent Bill Webster says the game should not be played on school grounds.
The same game made headlines late last month in Merrimack, N.H. Officials became concerned after a student backed out of his driveway and into a car that was blocking his exit, possibly on purpose. Police said the student who was trying to leave his driveway was a target in an "Assassin" game.