Wendy Kopp and Richard Barth are a power couple in the world of education, emblematic of a new class of young social entrepreneurs seeking to reshape the United States’ educational landscape by creating new schools, training better principals and getting more smart young teachers into needy classrooms. Kopp founded Teach For America, a nonprofit program that recruits elite college graduates to teach in low-income schools, and Barth runs the Knowledge Is Power Program, or KIPP, a charter school network.