The teacher would threaten the slipper but we children would refer to it more accurately as getting the pump.
I am the youngest of my family to attend that school. There is a fairly large age gap between myself and my siblings, interestingly my eldest sibling does not recall any teachers using a slipper in the classroom, they did sometimes use their hands. He does recall children (including himself) being sent to the head fairly frequently. It seems by the time I attended the school, teachers ( who were pretty much the same ones that taught him) had took to using classroom punishment more frequently while sending the pupils to the headless.