Don't Hit Your Kids

Clay Jones, a pediatrician writing for Science-Based Medicine, describes the research, such as it is, on spanking and corporal punishment, and the difficulty in defining what's abuse. He writes:

Spanking is most commonly used to discipline preschool and school-aged children, but sadly about 15% of children under the age of 1 year are spanked. This number is considerably higher in poor families, with about a third of infants being hit.

Women who experienced physical or sexual abuse, or were exposed to violence in the home, are much more likely to practice infant spanking and to have a positive view of corporal punishment in general. Children this young, and often even older kids, do not understand the connection between the physical punishment and the undesired behaviors, and even the vast majority of spanking proponents do not recommend it in babies.

Another fact I didn't know:

Laws regarding corporal punishment vary from state to state. 19 states currently allow the striking of a child in any school setting. Of the 31 states and the District of Columbia that ban the practice in public schools, only New Jersey and Iowa also include private schools. 

I thought corporal punishment had been banned in all schools. But 19 states still allow it, and almost all private schools could still have it.