One man hawking his idea for schoolroom security to the Michigan Police Chiefs convention in Grand Rapids this week is Rob Couturier, who has a metal plate with thick steel pins that stick into the floor and jam a classroom door shut "within a second".

He told WOOD TV that a teacher does not have to wait for a lockdown order from the principal to protect the classroom if trouble breaks-out in the hallway.

The Michigan Sheriff’s Association endorses the idea.