One hundred years ago, in 1920, the Royal Academy of Dance was founded in England by a group of aficionados that included the ballerinas Adeline Genée (Danish) and Tamara Karsavina (Russian). Even though England did not have a national ballet company at the time, classical dance thrived on its stages, even the less rarified stages that presented variety programs. “Ballet was still part of music-hall entertainment,” Eleanor Fitzpatrick, one of the exhibition’s curators, recently told The New York Times. With photographs, stage and costume designs, and artifacts, the exhibition embodies the 100-year history of British ballet, which reached its first pinnacle in 1946, with the Sadler’s Wells production of The Sleeping Beauty. —L.J.