If behaviour ran near at parallel levels among girls from non caning schools to girls’ schools that did adopt CP, then others punishment options seemed to work reasonably well enough for schools that didn’t cane.
The problem seems to identify itself where co-ed schools treated boys and girls differently, did these schools feel what worked well in girls schools, would work in a co-ed situation with the girls, hence girls were subjected to less CP or given alternative punishments. There could be no comparison for the boys, co-ed schools just followed suit, caning boys in similar numbers to all boys’ schools, because that what they adopted , overall boys were disadvantaged and the equality band widened.