Where, under the provisions of any act of Assembly, an election shall be held for and against the annexation of territory comprising a school district of the second, third, or fourth class, to a city comprising a separate school district, and, if it shall appear by the vote when counted that a majority has voted for said annexation and the result of said election shall have been certified to the court of quarter sessions having jurisdiction of the proceedings, the board of school directors of said annexed school district shall not thereafter make any change in textbooks, or adopt additional textbooks, or contract for any new school sites, or let any contract for the erection, enlargement, alteration, equipment, or furnishing, of any new school sites, or let any contract for the erection, enlargement, alteration, equipment, or furnishing, of any school building, without the approval of the board of school directors of the said school district of such annexing city.