A study that looks at why parents allow their teens to sip alcohol concludes they are more likely to permit drinking if they think their child’s friends drink, too.

“Parents may be supplying sips of alcohol in response to believing their child will be exposed to unsupervised alcohol use with their peers. However, they may be wrong in their belief, and may be prematurely introducing their children to a behavior that may have marked risks,” researchers write in Pediatrics.

About 60 percent of teens have tasted alcohol by age 13, according to AAP News. The researchers note sipping alcohol may be a stepping stone to additional drinking by underage teens. Parents are a major supplier of alcohol, they found. Drinking by minors is associated with delinquent behavior and poor health, they add.

A study published last year found children who are allowed to sip alcohol are more likely to drink by the time they reach ninth grade.

Researchers at Brown University found children who had sipped alcohol by the time they were in sixth grade were five times more likely to have a full drink by the time they were in ninth grade. They were four times more likely to binge drink or get drunk, compared with teens who hadn’t sipped alcohol when they were children.