Often when a kid was getting a spanking in public the adulits present would show their approval and support for the punishment often culminating in an enthusiastic round of applause when it was at an end!
A side from one instance in the US when a drunken lout of a father, a co-worker of my father whom he had to be on good terms with, thrashed and beat his son in our hearing. It was pitiful to hear and showed what a p.o.s the guy was.
But aside from that I never witnessed anyone getting spanked in public when I was young or in my 20s or even 30s. I have the impression that was thought to be vulgar and low-class behavior on the part of parents. Perhaps punish at home, but never in public. Talking about Belgium here.
But once, in a somewhat comical instance, we were with our foster son in Granada Spain in the square in front of the cathedral. He was then around 5, almost 6. Anyway, he was a bit fretful and my wife started to admonish or chastise him in some way. Not spanking, but maybe talking disapprovingly in a loud voice or manner, maybe dragging him forth. Something like that.
Then an old Spanish lady, a grandmother looking type clad all in black went up to my wife and read her a riot act in Spanish, wagging her finger angrily at my wife and patting our son on the head and giving him a big smile. My wife turned red and I started laughing because I did find her at times too needlessly strict on trivial matters. Our son grinned a huge wide smile while we walked away, with the Spanish lady reading my wife a Spanish version of the good parenting riot act and giving my wife the evil eye.
I thought it hilarious actually.
And I conclude from that that kids are probably not spanked in public in Spain. And for all that, they are very well behaved and polite in my decades of experience in Spain.