Emily Kingsley is a retired writer for “Sesame Street,” the PBS TV show and nonprofit educational organization. The parent of a son with Down syndrome, she and her husband were determined to give him the most enlightened education possible, at a time when individuals with Down syndrome were assumed to be ineducable — with great results. Kingsley started incorporating her son into “Sesame Street” scripts, which led to inclusion of people with disabilities and disability curriculum into the TV show’s format. She wrote scripts, books, and songs for Sesame Street for 45 years, winning 23 Emmy Awards. Kingsley and her son are featured in the documentary film Far from the Tree.