When we mover up to the 4th form (age 11) in primary school, Our class teacher was also the gym teacher for the 4yh year boys. On the first gym lesson we were told that if any boy forgot his kit, the school had lots of spare and it could be hired at a cost of four firm smacks with his gym plimsol.
If any boy had pants under his gym or football shorts then we would receive three firm smacks with his plimsol and any misbehaviour in the gym or changing rooms would be one to two smacks with the slipper and then we were told that the last boy in the gym would be slippered and the last boy to leave the changing room after gym would be slippered.