I’m not so sure about a less “severe” form of CP but certainly less “serious”. I’m not sure if you’ve seen my previous posts on this subject so, to clarify, I don’t treat “serious” and “severe” as synonymous. The slipper can hurt a lot and the cane does not, necessarily, hurt more than the slipper. The slipper can be just as severe as the cane. The difference, as I see it, is that the slipper was an “everyday” punishment whereas the cane was only used by headteachers and was reserved for especially naughty girls (and boys). That made it a more “serious” punishment.
This “two tier” system had some advantages that appear to be absent from the Scottish system. In England, minor, everyday, misbehaviour could be dealt with by any teacher with his/her slipper. Serious matters were dealt with by the Head. with his/her cane.