Students arriving for class this afternoon at the John Jay College of Criminal Justice building at 445 West 59th Street were greeted by a worker using a bullhorn to warn them: Stay away! Bed bugs! Classes canceled! Basically, the school's gripped with panic and they're one step away from painting a giant red "B" on the front door. After employees complained of itchy rashes this week, the administrators called in one of those trained dogs, who turned up the pests on the first three floors.


