Graduate School of Education professor emeritus Gerald S. Lesser, a legendary educator and curriculum developer for the children’s television show “Sesame Street,” died on Thursday. He was 84.

Lesser—described by former student Joseph H. Blatt ’70 as a “real visionary who didn’t stop innovating”—joined the Ed School faculty in 1963, where he taught developmental psychology and its application to education until he retired in 1998.

Lesser chaired the Ed School’s Human Development Program, which had focused entirely on cross-cultural studies of child rearing.

Over the following decade, Lesser added faculty in many other specialties more directly related to educational practice, including educational television.

“He crossed the boundary from research to practice,” said Education Professor Sara Lawrence-Lightfoot, who described Lesser as a “pragmatist.” “He was interested in what he knew and how he could use that knowledge to change the world.”

While at Harvard, Lesser also served as chairman of the Children’s Television Workshop’s board of advisors from 1969 to 1996. In 1974, Lesser published a book, “Children and Television: Lessons from Sesame Street.”

“He was instrumental in forwarding the idea of ‘edutainment,’” said Ed School graduate Charlotte F. Cole, vice president of international education, research, and outreach at what is now called the Sesame Workshop.

“He was instrumental in building the Sesame Workshop model, which was the bringing together of educators and researchers to work directly on a production process,” she said. “They were actually members of the production team.”

“At a time during the 1970s when the Ed School had serious financial problems,” said Ed School Professor Emeritus Robert A. LeVine, “‘Sesame Street’ stood out as its outstanding contribution to American education—though it was not directly related to American public schools.”

Lesser’s devotion to his work with children, particularly those from disadvantaged backgrounds, was evident in his persistence in developing programming material that would help give all children a chance to develop and reach their highest potential.

“He really saw ‘Sesame Street’ as a vehicle for giving all children a chance [to learn] in a way that was fun and engaging and meaningful to them culturally,” Cole said.

Lesser had an “excellent sense of humor” and had the ability to get people to communicate across their various areas of expertise, according to Blatt, director of the Ed School’s Technology, Innovation, and Education Masters Program.

“He taught us that researching, designing, producing, and testing learning materials for 4-year-olds requires every bit of creativity, dedication, and wisdom that we could muster,” Blatt wrote in a tribute to his mentor, “and that the work is more rewarding and more fun than we could have imagined.”

Ed School Dean Kathleen McCartney holds the Gerald S. Lesser Professorship in Early Childhood Development.

“The first time I met Gerry Lesser, he joked that he was sorry to have saddled me with the name ‘Lesser Professor,” McCartney wrote in an e-mail to the Ed School faculty and staff. “[H]e also told me how proud he was that the dean of the school was serving in the chair that honored him. But I am the one who is proud to carry his name along with mine.”

“When I first saw a Harvard professor laugh out loud at Cookie Monster, I was hooked,” Blatt wrote in his tribute, “and as Gerry’s friends and students will understand, I learned that you could do important work while wearing sneakers everywhere.”

Lesser is survived by his wife, his children and their families.

—Staff writer Xi Yu can be reached at xyu@college.harvard.edu.