The strap didn’t deter anything. You did, in fact, try to rob the store full well knowing that “a boy who was caught stealing from a shop and reported to the school would almost certainly be severely strapped.”
If CP did deter effectively, it would not have been used so extensively or frequently with boys in schools like yours. Claim it is a penaly for a misdeed and I will give you no argument but you have not shown that it is a deterrant only something that was significantly feared by some boys when the threat of its inevitablity was clear. And this clarity would only come AFTER the misbehavior and the apprehension had occurred.
How can someone possibly claim CP had a deterrant effect when is was used so commonly, so frequently and so routinely for the same behaviors over and over again often with the same boys or with boys who clearly saw through observation that other boys were corporally punished for those behaviors. That claim strain credibility and a number of well established psychological principles