DC, especially right near GULC's campus, is really expensive. $1,500 might be a stretch even for a small 1-bedroom if you want to be walking distance from class. Further out you'll have better luck. In the district I've been pointed to the Adams-Morgan and Mount Pleasant neighborhoods. The close in Maryland suburbs like Silver Spring and Takoma Park are supposedly very nice, reasonably priced and easy to get in from on the metro. In Virginia you'd have to go a little further out to get cheaper stuff; the commute may involve a drive.
The Washington Post has the best apartment finder I've found for the whole area. You can even search by distance to a specific metro stop. http://www.washingtonpost.com/rentals/?nid=top_rentals
Full disclosure: I'm not from DC but have family there and know the city a bit. What I said is based on that, looking for a place myself the last month, and what natives I've asked have told me.