In any city having a population of less than 20,000 which is operating under a special act and whose public schools within its corporate limits are governed by virtue of this special act, upon a petition signed by a majority of the electors in any territory which has been heretofore or may be hereafter annexed to the city for general corporate purposes, the annexed territory shall be included in and subject to the control and government of the city for school purposes as fully as if the annexed territory had been originally within the corporate limits of the city. The territory, when so annexed, shall be thereby disconnected from any school district of which it was a part prior to the annexation.
     The city may levy and collect taxes for school purposes in the annexed territory in the same manner and to the same extent as in the territory comprised within the original corporate limits of the city.