Property exclusively for school purposes.

That parcel of land marked and designated upon the map of the City of Washington as part of lot No. 11, in square No. 141, beginning at the northwest corner of said lot, and running thence due south on the west line of said square, 50 feet; thence due east, 30 feet; thence due north, 50 feet; thence due west on the north line of said square, to the point of beginning, and also that piece of land marked and designated upon said map as a public reservation, located between 8th and 9th Streets and K Street and Virginia Avenue Southeast, known as the Anacostia engine house, together with the buildings and improvements thereon, are severally set apart and appropriated for the use of the public schools in the City of Washington, so long as they shall be occupied for that purpose, and no longer.