All taxes for public school purposes heretofore levied or assessed by or through the instrumentality of the board of public education in any school district of the first class in this Commonwealth, which, for any reason, or in any manner, or to any extent, exceeded the millage or amount which might have been levied or assessed validly, or otherwise exceeded the power of the board that acted in the matter of such levies or assessments, are hereby ratified, validated, and confirmed, with like effect as if the General Assembly itself alone had annually levied or assessed said taxes and had determined the amounts thereof.