Someone asked a similar question a week or two ago:
http://www.dcurbanmom.com/jforum/posts/list/638529.page
This year (2017) is the first graduating class of 15 8th graders. There are graduating 8th graders going to Banneker, Duke Ellington, and several other high schools next year.
6-8 grade next year will still be <25 kids per grade. Next year's 5th grade should have a full cohort (for ITS) of 50 or so kids per grade.