Sligo Creek Coop is almost half teens (grades 7-12) of its 110 students. It is on upper 16th st in NW, but it is closest to the Silver Spring metro with either a short bus ride or long walk on the S2 bus. It was formed by DC/lower MoCo parents who wanted to keep homeschooling with teens.
What classes do you have left? Also, there is an African American homeschool teen group in DC.
If you kid is willing to do robotics, then there is a homeschool group near New Carollton metro.
Does your kid play soccer? In DC, we still have pretty good coed HS rec divisions in the Stoddert league which mostly plays close to the Tenleytown metro.