In order to consolidate Federal holdings in, and to improve, Colonial National Historical Park, the Secretary of the Interior, when he finds that the public interest will be served thereby, is authorized to accept on behalf of the United States from the York County School Board, State of Virginia, the conveyance of any land or interests in land located within the authorized area of the Colonial National Historical Park, together with the structures situated upon such properties, as may be agreed upon by the Secretary and the school board; and, in exchange therefor, to convey on behalf of the United States to the school board not more than fifty-five acres of land or interests in land situated within the Colonial National Historical Park.