Whenever any school district of the fourth class has increased its indebtedness, with the assent of the electors of such district, in accordance with the provisions of an act, approved the twentieth day of April, one thousand eight hundred seventy-four (Pamphlet Laws, sixty-five),¹ entitled “An act to regulate the manner of increasing the indebtedness of municipalities; to provide for the redemption of the same, and to impose penalties for the illegal increase thereof,” and the amendments and supplements thereto, and the purpose for which said increase was asked and assent obtained has proved to be impracticable or undesirable, the board of school directors of any such school district may, by their resolution or vote, signify a desire to use the money, so borrowed or authorized to be borrowed, for any other lawful purpose, and such other purpose may include the erection of a joint school building with another school district, or the building of an addition to an existing school building; and the said moneys, so borrowed or authorized to be borrowed, may be used for such other purpose, if the assent of the electors thereto is obtained as herein provided.