24 Pa. Stat. § 6-603
There shall be but one levy of school taxes made in each school district in each year, which shall be assessed, levied, and collected for all the purposes provided in this act, and shall be uniform throughout the territorial limit of each school district, except that those school taxes which school districts are empowered to levy under the authority of the act of June 25, 1947 (P.L. 1145), as amended, may be levied at any time during the period authorized for the assessment and levy of any school taxes: Provided, That (1) where two or more school districts have voted to become a union school district in accordance with the provisions of this act and prior to the actual creation of the union school district, the school board members by a majority vote of all the members comprising said school boards shall assess and levy a uniform school tax in all of the districts comprising said union school district for general revenue purposes necessary to operate said union school district commencing the first day of July following the vote establishing said union district, and (2) whenever hereafter a school district of the second, third, or fourth class shall be annexed to and merged in, and become a part of a school district of the first class or first class A, or shall be merged into and become a part of a school district of the first class A as a reorganized district under the provisions of Article II, subdivision (i) of this act, the board of public education of said school district of the first class or first class A shall have power to levy a special school tax on the territory which comprised said annexed and merged school district or on the territory which comprised the school district merged into and becoming a part of a school district of the first class A as a reorganized district, to provide for the expense and maintenance of the schools thereof from the end of the school year of said annexed and merged or merged by force of reorganization school district to the beginning of the next school year in said school district of the first class or first class A, and to provide for and pay the floating indebtedness of said annexed and merged or merged by force of reorganization school district. Said levy shall not exceed one-half of the last previous total annual millage levied by said school district of the first class or first class A.
24 P.S. § 6-603