For the year one thousand nine hundred fifty, and annually thereafter, every school district of the first class shall levy and collect an annual tax in the manner and at the rate hereinafter set forth: Provided, That in school districts of the first class coterminous with cities of the first class, for the year 1968, and annually thereafter, if authorized to do so by city council of the said city of the first class, every such school district of the first class coterminous with a city of the first class, shall levy and collect an annual tax in the manner and at the rates hereinafter set forth. Such tax shall be in addition to any other tax every such school district is empowered to levy and collect under any existing law. The taxes and penalties collected under the provisions of this act shall be used by every such school district for general public school purposes.