Day co-founded the school in 1944, and in 1961 she instituted annual performances of The Nutcracker, which became a holiday favorite with local audiences. Generations of dancers training at the school had the opportunity to dance as party girls and soldiers in Tchaikovsky's popular ballet.
According to the school's website, notable alumni include dancers such as Virginia Johnson, Kevin McKenzie and Amanda McKerrow, as well as actresses Shirley MacLaine and Georgia Engel. Students have been awarded medals and recognition at the Prix de Lausanne, the Moscow Ballet Competition and the Varna (Bulgaria) and New York International Ballet Competitions.
Day did dance herself, but she concentrated on teaching; according to the Post, she was legendary for her ability to spot the tiniest of imperfections.
She was a native of Foggy Bottom (the area near the Pentagon) and began her formal training at 11, according to the paper. She studied in New York and Europe, but her biggest influence was former Anna Pavlova company dancer Lisa Gardiner, with whom she founded the school. She became sole director when Gardiner died in 1958 and officially retired in 1999.
Day created the respected Washington Ballet company in 1976. She is credited with bringing world-famous dancers to Washington and building the profile of ballet in the nation's capital.
She was an only child who never married or had children and who devoted her life to dance. She died of complications from heart disease at home in Washington, according to the Post.