It definitely depends on how conservative the congregation, the surrounding area, and the parents are. I was in a fairly laid-back congregation for most of my time in NY, and it hardly ever happened. When I switched to the Russian congregation--mostly made up of American Bethelites and Pioneers--there were very few kids in the congregation, but those kids got beat all the time.
The WTS doesn't explicitly encourage spankings, as it used to--most likely due to legal issues. The practice lives on in the oral tradition, however, and the WTS has done little if anything to discourage it.