The ‘Sleeper’ game, where an older child covers the nose and mouth of a younger pupil until they pass out has left at least one child in hospital.
Greater Manchester Police North have alerted parents to the danger on their Facebook page.
A message said: “Attention all parents/guardians. We have received reports of a new craze called ‘Sleeper’.
“This involves children completely covering the mouth and noses of younger children until they completely pass out.
“This is extremely dangerous. A child is currently in hospital being treated after falling victim to this game.
“Please advise every child you know and warn them of the dangers. This could easily lead to concussion or even death.”