The National District became the Capital Conference. The eight teams are: Edison, Falls Church, Jefferson, Lee, Marshall, Mt Vernon, Stuart, and Wakefield.
The National District was disbanded beginning with the 2013-2014 season When active, it comprised eight teams: Edison, Falls Church, Hayfield, Mt. Vernon, Stuart, Wakefield, Washington and Lee, and Yorktown. Edison, Wakefield, Washington and Lee, and Yorktown have all-weather artificial turf fields.
Here is a link to National District history in a Wikipedia article.
Here are links to the athletics home page for each of the former National District School:
Edison Contact Info
Falls Church Contact Info
Hayfield Contact Info
Mt. Vernon Contact Info
Stuart Contact Info
Washington and Lee