In 1969, the children's television show Sesame Street premiered on the National Educational Television network (later succeeded by PBS) in the United States. Unlike earlier children's programming, the show's producers used research and over 1,000 studies and experiments to create the show and test its impact on its young viewers' learning. By the end of the program's first season, the organization founded to oversee Sesame Street production, Children's Television Workshop (CTW), had developed what came to be called "the CTW model": a system of planning, production, and evaluation that combined the expertise of researchers and early childhood educators with that of the program's writers, producers, and directors.