I'm from the Dc are so I'm somewhat familiar with what he's asking. Supposedly a few years back, Congress passed an act that made DC residents at every state school in the United States for tuition purposes. This is supposed to be a compromise for not granting DC statehood (and thus keeping it 'nonpartial' in gov't matters).
I was beyond college-age when this happened (plus I was not actually a DC resident). I believe the poster is asking about this.