A rare, salacious lawsuit against the elite DC private school drags high-profile Washingtonians into unwanted limelight and airs graphic e-mails from the psychologist who taught sex ed at the Obama daughters’ school. The exceedingly messy lawsuit is headed for trial—and the circle of high-profile Washingtonians wrapped up in the case is expanding. A Sidwell official claims a school psychologist had an affair with his wife while treating his daughter, then five, and that Sidwell took “flagrant and outrageous actions” that allowed the “open sexual relationship.” For Sidwell—an elite private school in DC with an annual tuition of around $34,000—the lawsuit...