Most of these discussions are silly. What worked for one parent or rebbe might not work for another. There are also halachos here, some of which were recorded in prior comments. Additionally, there are hadrachos from our contemporary gedolim that are useful. It is easy to generalize from one situation to another, to create rules from certain experiences, to use specific instances to conclude a self-made halacha. These are all follies, and שומר נפשו ירחק מהם. None of us were trained in parenting before having children, and it is the exceptional rebbe who received training in such matters before being hired to teach in a classroom.
Petch is not intended to cause pain, as is clear in the gemora. It is to make a point in action that failed to transmit in words. In a wide variety of seforim on the halachos of chinuch, relevant to parents and mechanchim, there is a wealth of wisdom from Gedolei Yisroel throughout the generations. It is clear that the potch that punishes is not the one that teaches. That is clearly outside of the potch that is muttar in halacha. The first potch, under a list of conditions may be permitted (not necessarily recommended). The second one is a physical assault, and is a violation of Torah Law.
There are many more aspects to this that provide fodder for lively discussion. I have no problem with anyone attacking what I wrote. I did not contrive anything. Everything came directly from our Torah giants. If anyone wishes to move this thread into a debate, I respectfully ask that one provide direct references from the seforim of halacha. If we go there, I will share direct quotes supporting every word I wrote.