For instance, people should be careful not to accept social media invitations from anyone they don't know, she said.

"You wouldn't let a stranger in the house," Armacost said. "You shouldn't let a stranger into your Facebook life. This is a distinction that a lot of adults have trouble making, let alone children."

"Social media use requires that we learn appropriate boundaries," Evins said in a statement. "It is a life skill that requires our thoughtful attention and collaboration with our families as we educate the whole child."

A spokeswoman for the school, which has about 400 students, declined to comment further, citing the police investigation.

This story has been updated.

Baltimore Sun reporter Liz Bowie contributed to this article.