There were plenty of spankings at the KH's I attended for sure....the one in CT, I think, had less of that than the one in IL. It seems that each congregation has it's own personality that is derived from the PO, elders and other strong-minded individuals.
As for real beatings, I think most that suffered those did so at home for the most part. I knew of one elder who used either a belt or an actual rod on his kids that left bruises on their backs, rear ends and thighs. From what I understand, he was always consciously careful to hit them where it wouldn't be visible...and I certainly don't remember ever seeing his kids sporting bruises, so he was successful in hiding what he was doing. I don't think anybody knew about it until he and his wife were having marital problems and she spilled the beans to some sisters...not sure if she told the elders about it or not.
There was another elder who was pretty rough with his stepsons...guess one time he really lost control in front of a young guest who was visiting from TX and the boy went back, very troubled, and related what happened to an elder in his congregation who also had ties to the IL congregation. I know he called and talked to the PO (a big Mr. Do-nothing if there ever was one), as well as the elder who was doing the beating. I doubt it did much good, other than to make said elder more careful.
