(a) For the year one thousand nine hundred forty-eight and annually thereafter, every school district of the first class A shall issue mercantile licenses and levy and collect an annual mercantile license 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 license fees, taxes and penalties collected under the provisions of this act, shall be used by every such school district for general public school purposes.

(b) On and after the first day of January, one thousand nine hundred fifty, in any school district of the first class A which, after such date, has no authority to levy or does not levy the tax imposed by this act, the collector is authorized to and shall continue to collect delinquent taxes owing such school district under any levy for any prior year, under the provisions of this act, until such taxes are either collected or until the collector is exonerated with respect to such taxes. The delinquent taxes so collected shall be used by every such school district for general public school purposes.