by Jean Twenge (@jean_twenge) Editor’s Note: This essay is excerpted from Rule #2 of 10 Rules for Raising Kids in a High-Tech World (the full chapter also includes how-to tips). When Diana Park’s daughter was in 7th grade, she got her first smartphone. The middle-schooler knew she was not supposed to be on her phone after bedtime. But then, late one night, Diana heard her daughter talking and went to investigate. Her 12-year-old was FaceTiming with a friend at midnight—a good three...