A thousand miles from Newark, in a tiny old school building tucked behind a Christian church, Cary Booker delivered the bad news. It was spring of 2011, and Omni Prep Academy, the Tennessee charter school co-founded and led by U.S. Sen. Cory Booker’s older brother, could no longer pay its kindergarten and first-grade teachers, the elder Booker announced, according to former teachers who were in the room. The financial woes weren’t a shock — when the school opened the previous fall it provided no books, no curriculum and almost no training for its novice educators, former teachers said in interviews...