I was recently talking to a father of two kids, ages 5 and 6. He told me he and his wife decided to wait until the children are in high school before even considering giving them access to social media.

He’s not only a concerned parent. He’s U.S. Surgeon General Vivek Murthy, who last month issued an advisory about the effects of social media on adolescent mental health.

“Early adolescence is an especially risky time during a vulnerable stage of brain development,” he told me. “Kids are much more susceptible to peer pressure, opinions and comparison.”

Congress passed a law in 1998 called the Children’s Online Privacy Protection Act. It was intended to keep companies from collecting and disseminating data on children under age 13. So developers have used it as a key age to allow kids to create accounts, particularly for services with an advertising component.