Whenever it shall appear, in any case hereinafter enumerated, that the population of any school district in this Commonwealth is such that it should be included in another class of school districts, the Superintendent of Public Instruction shall issue a certificate to said school district to that effect, and such school district shall, with the beginning of the next school year after said certificate has been issued, become a school district of the class to which it properly belongs. The provisions of this section shall apply when:--
(1) The Superintendent of Public Instruction, after the taking of each United States census, has canvassed the same, so far as it relates to the population of the several school districts, which he is hereby required to do;(2) Territory comprising a separate school district is annexed to a city, borough, or township, and the decree of the court or the vote of the electors effecting such annexation has been certified to the Superintendent of Public Instruction;(3) Territory has been annexed to a city, borough, town, or township, and enumeration of the population of such annexed territory has been made.1949, March 10, P.L. 30, art. II, § 205.