At the end of 2014, Tulsa, Oklahoma, sixth-grade teacher Melissa Bour received a friend request on Facebook from one of her students. She didn’t accept the request, but after a quick look through the girl’s friends list, she saw the names of dozens of kids from her classroom. Many of the student’s Facebook pages were completely public, meaning even strangers could search through the kid’s personal photos and messages.

  “I saw students dressed improperly and dirty language,” Melissa says. When she brought up her discovery in class, the students were unfazed. So she created a post of her own.

She wrote a letter on her Facebook page, “Dear Facebook: My 12-year-old students think it is ‘no big deal’ that they are posting pictures of themselves...Please help me...show them how quickly their pictures can get around.”

       In hours, it was shared 108,000 times across dozens of states and four countries. She deleted（删除）it after eight hours, but it continued to get around. “I wanted to show them that it’s on the Internet forever,” she says.

      As she explained the results of her experiment in class, the student’s eyes got bigger and bigger. “It scared（使恐惧）a few of them into deleting their pages completely,” she says. “Others have deleted improper posts and used privacy settings to manage their pages.”

      Her purpose wasn’t to scare them off social media（社交媒体）but to push them to be mindful of what they post. Melissa says, “I tell them, ‘Just because everyone else is sharing doesn’t mean you have to.’”