In the last two-and-a-half decades I've labored with lots of K-12 instructors to arrange student outings to Washington D.C. This spring I received a thanks letter from Shawn Tierney, an instructor at Santa Rita Senior High School in Tucson, Arizona, detailing specific facets of a vacation to Washington D.C. that managed to get a "resounding success." Have a look at
washington dc tours for more information.