When it comes to teachers and students, there is no such thing as consensual sex, experts said yesterday. The power differential is too exploitative in those sexual encounters, said Charol Shakeshaft, a former Hofstra University professor who now teaches educational leadership at Virginia Commonwealth University and is an expert on sexual abuse in schools. "It's a violation of trust and professional boundaries," Shakeshaft said of the March 20 encounter Nassau police say happened between Heather Kennedy, 25, a math teacher at Wantagh High School, and a 16-year-old boy who is a student at the school. Kennedy was arraigned yesterday on...