NEW YORK, JULY 30 -- Joan Ganz Cooney, who helped create the company that produces "Sesame Street" and other educational series, will step down as chief executive of Children's Television Workshop this fall, the firm announced today.

Cooney, 60, who will become chairman of the executive committee of the company's board of trustees, will be succeeded by David Britt, currently president and chief operating officer.

"This seems to me the right moment in CTW's life and my own to make a change," Cooney said. "I look forward to continuing to work with David and all of the other talented people at CTW."

Besides "Sesame Street," a program seen on more than 300 stations of the Public Broadcasting Service, the company also produces "3-2-1 Contact," a science program, and "Square One TV," a mathematics show.

In 1966, Cooney undertook the feasibility and planning study for the Carnegie Corp. that led to the creation of "Sesame Street." She was elected president and chief executive officer when the company was incorporated as a nonprofit organization in 1970. She was elected chairman-CEO in 1988.

Britt, 53, joined the company in 1971, following work in Washington for the Agency for International Development, the Equal Employment Opportunity Commission and the Overseas Private Investment Corp. In 1974 he became assistant to the president, and in 1988 he was named president and chief operating officer.