No, it didn’t happen overnight – it took a couple of years. But it did happen. There was a massive deterioration in overall behaviour in schools in the UK in the years following abolition, and the deterioration was far more dramatic among boys than girls. The same has been seen in nearly all jurisdictions have occurred in the last thirty years.
I think it took more than a couple of years, there was over a decade to compare decline before CP in private schools ceased. Parenting, Social conditions, children’s rights and the schools themselves , have changed considerably; all have an impact on children’s approach to authority and behaviour.