Over the winter, Mira conducted a “room refresh,” parting with childhood objects and getting more grown-up ones. Mira’s sibling, Dylan, is not allowed to hang out in Mira’s room. “If they do, I will shun them,” Mira said. “I will go—HYAH!—get out.” The last time I hung out with sixth-grade girls, it was 1999, and I was one. Kids wore low-rise jeans, collected Absolut ads and Sanrio stickers, read Seventeen magazine, and nursed Spice Girls-themed Chupa Chups lollipops.