Once upon a time – a time you probably don’t remember if you’re younger than 30 – American schools sought to teach children self-control, personal responsibility, and respect for others, especially adults. Students were corrected when they made mistakes and reprimanded when they slacked off or talked back. Most unfathomable to the current education establishment, teachers assessed students on qualities such as “gets along well with others” – and some children actually flunked. In the eyes of schoolteachers and parents, shaping kids into productive and responsible citizens was more important than protecting their egos. Then, sometime in the 1970s, schools...