Ten years at an English public school do not encourage dreaming. Georgie won his growth and chest measurement, and a few other things which did not appear in the bills, under a system of cricket, football, and paper-chases, from four to five days a week, which provided for three lawful cuts of a ground-ash if any boy absented himself from these entertainments.
This is from "The Brushwood Boy" by Rudyard Kipling.
I don't understand the meaning of
lawful cuts of a ground-ash
I am glad if someone would kindly teach me.