I actually think smacking very be very effective. It has to be clear, controlled, and a known final resort. It works between the ages of around 3 and 8, although that varies for different children
I don't understand these parents who look in horror on smacking, then shout at their kids. I think shouting is far worse, tbh. Smacking can be done with a quiet explanation, and clear, precise way, and is over immediately. Shouting is far more damaging, and disturbing for young children, and the mood lasts far longer.
I was a smacked child. I smacked my eldest two sons. I recorded it in my diary, one got 3 smacks between 3 and 8, and the other got 5.
I didn't smack my youngest son. Times had changed, and it is no longer culturally appropriate.
There are other ways, as long as punishments are swift, firm and entirely predictable, removal to room, confiscation of item, etc, then it still works. Never shouting though.
I have shouted at my children a couple of times, also recorded in my diary.. not through deliberate, considered choice though, but through anger and temper.
I am a teacher, and sometimes shout at school - that is for much older children, teens, and is always a deliberate, considered choice.