By Alice Park, Time

Fifteen-year-old Taylor Santos let a classmate copy her homework, and she learned the hard way never to do it again. Santos, a student at Springtown High School in Texas, was punished by a vice principal with a swift swat to her bottom using a wooden paddle. The spanking left blisters and forced her to sleep on her side that night.

As upset as Santos’ mother was, however, it wasn’t the spanking, which she had consented to, that led her to complain to the school board. It was the severity of the punishment and the fact that it was delivered by a male administrator, contrary to the district’s policy that only teachers of the same gender as the student may mete out corporal punishment.

Across the U.S., Santos’ case and that of another student in the same school have fired up parental passions over whether corporal punishment should be allowed in schools at all. Nineteen states permit it, but researchers say there is little evidence that spanking actually works to change children’s behavior for the better.

In fact, kids spanked by their parents tend to be more aggressive than other kids and are likelier to develop behavioral problems as they get older; some studies show that corporal punishment can even lead to lower IQs. “The more kids are spanked, the more problematic their behavior is,” says Elizabeth Gershoff of the University of Texas at Austin, who has conducted the most comprehensive analysis to date of studies on corporal punishment and its outcomes.

Still, some experts say that because most of the research on spanking focuses on punishment at home, not in schools, it’s unfair to assume the effects are the same. It’s also possible that the studies aren’t measuring the impact of the punishment at all but instead simply reflect the fact that disobedient children who are disciplined are more likely to have behavioral problems in the first place. These experts point to studies showing that even nonphysical alternatives like verbal scolding don’t lead to positive changes in behavior among children.

Then there’s the issue of finding the line between discipline and abuse, which is hard enough for parents punishing their children to define and defend, never mind for non–family members like teachers. That’s what prompted Santos’ mother to speak out; the vice principal, she feels, just went too far.

In response, the Springtown school board decided to make changes to its corporal-punishment policy. Under the old rules, parents had to opt out of corporal punishment for their kids; now they must provide written permission for it to be administered. And parents can specify whether they want the punishment to be delivered by a male or female teacher, although an official of the same gender as the student must witness the punishment no matter what–meaning two adults will always be present.

For some experts, having to go to such lengths to make corporal punishment acceptable supports the idea that it doesn’t belong in schools at all. They say exposing children to any type of violence, at home or in school, can simply be too harmful.

Dozens of countries have taken a simpler approach, banning all forms of corporal punishment against kids, even if it’s administered by parents. While the U.S. Congress is considering such a ban in schools, the final vote — on the Hill and in the classroom — is uncertain.