It was called Extended School Year. The program has ended. The schools were:
"In addition to Turner and Raymond, the schools participating in the program include H.D. Cooke Elementary School in Ward 1 and Randle Highlands and Thomas Elementary School in Ward 7. Ward 8 schools include Kelly Miller Middle School, Garfield Elementary School, Hendley Elementary School, Martin Luther King Jr. Elementary School, and Hart and John Hayden Johnson Middle Schools. There are 3,600 students attending the year-round schools." from this article
https://afro.com/d-c-public-schools-start-year-round-program/.