Google Street View.
I decided to look into it, and it turns out the place (770 Park Rd NW) is Nationhouse, which has two African-centered schools - Watoto School for PK-4th grade, and Sankofa Institute for 5th-12th grade.
Their website says they were "founded in July 1974 in Washington, D. C. NationHouse grew out of the student activism of Howard University community in the late 1960s" and they do "Afrikan centered education" which "provides opportunity for the study of all academic subjects from the point of view in which the history, contribution and future of Afrikan people is central."
I don't see any connection to the Sankofa coffee shop I wrote about it - Sankofa is a word that means, basically, taking from the past to make positive change. So, there you have it.