The Secretary of the Interior is authorized, in his discretion, to accept on behalf of the United States from the York County School Board, State of Virginia, title to approximately one-half acre of land in Nelson District, York County, Virginia, situated within the authorized boundaries of the Colonial National Historical Park, and in exchange therefor to convey by deed, on behalf of the United States, to the school board approximately one-half acre of land of approximately equal value situated within the Colonial National Historical Park.