A 19th-century illustration of a boy receiving a spanking, which...

A 19th-century illustration of a boy receiving a spanking, which today is banned in more than 30 nations. Credit: Universal Images Group via Getty/Universal History Archive

It’s odd: You’re having dinner with friends in a nice restaurant. One of them reaches for the breadsticks and carelessly elbows his water glass, swamping the tablecloth.

Immediately, his concerned fellow diners express solicitude and reassurance in response to the abashed offender’s apologies. Spare napkins are offered to stem the flood. In no time the water glass is replaced and normalcy restored.

But when a kid does the same thing, in many families the immediate consequence is a swat or a slap or, at best, a severe public reprimand.

What accounts for this discrepancy in how we treat children and how we treat adults?

In fact, apart from boxers and hockey players, children are the only members of our society whom we hit with impunity.

Men often used to get away with hitting women, but our society has appropriately clamped down on that deplorable practice. But with children, we not only permit the hitting, we sometimes encourage it.

Recently Missouri’s Cassville school district reversed its ban on corporal punishment and will now allow “swatting the buttocks with a paddle” when “alternative means of discipline have failed.”

Younger students are limited to one or two swats; older students can be swatted up to three times. Which is slightly counterintuitive; our society outlawed corporal punishment for adults long ago, but in school the older you are the more you can be hit.

Cassville isn’t an outlier: 19 states, mostly in the South and West, permit corporal punishment in public schools.

But most youngsters are more likely to be hit at home than at school. In fact, we spank our kids a lot.

One study from the University of North Carolina at Chapel Hill indicates that the “spanking rate” for 3- to 5-year-olds is 80%.

More recent polling indicates that the incidence of spanking is decreasing. The journal JAMA Pediatrics reported a drop in the proportion of parents who spank from 50% in 1993 to 35% in 2017.

This is a move in the right direction, but not all parents — or public schools! — have gotten the message. Spanking is a regular element of many children’s childhoods.

Some parents justify spanking by arguing that children need discipline. They turn to our Judeo-Christian tradition for support. Proverbs 19:18, for example, says, “Chastise your son while there is hope for him, but be careful not to flog him to death.”

The limitation in the second clause is good advice, but it sounds more like the sentiments of an entitled, overbearing patriarch than those of a loving god. A few lines away, the writer muses: “ … a nagging wife is like water dripping endlessly.”

For spankers, the Bible provides a rationale rather than a reason. I suspect that the real reasons we spank our children have more to do with the power relationship than with judicious attempts to discipline. We spank them because we can.

Combine that idea with the fact that nearly all spankings are fueled by anger and frustration, and the result is an unhealthy environment for many American children.

For decades, the American Academy of Pediatrics, the professional organization of 67,000 pediatricians, has been emphatic: It “strongly opposes striking a child for any reason. Spanking is never recommended.”

This position is grounded in research that indicates that any corporal punishment is linked to bad consequences for children.

In 2002 Elizabeth Gershoff, then of Columbia University, conducted a meta-analysis of 88 studies that identifies a correlation between “ordinary spanking” and bad outcomes, even when abusive practices — beating, kicking, burning — are factored out.

What sort of bad outcomes? A study of 2,500 children, conducted by Catherine Taylor of Tulane University, found that spanking is a strong predictor of aggression, defiance, temper tantrums, frustration and physical abuse of other children and animals.

This explains why more than 30 nations have banned spanking, at school or at home. In the United States, we are unlikely to pass laws that interfere with how parents treat their children at home.

But, at the least, the discredited practice of spanking should have no place in our public schools.