For decades, school districts have sorted students into neat grade groupings: K–5, 6–8, 9–12. But those lines have blurred. Some districts are reviving stand-alone middle schools. Others are phasing ...

At Middle School 50 in Brooklyn, New York, principal Benjamin Honoroff and his students are pumped to start the day — a dramatic transformation from when he came in a decade ago. "We were on a list of ...