In order to conserve the financial resources of the school district, neither the legal voters nor the board of education thereof, without the assent in writing of the commission, shall issue or authorize the issuance of notes or bonds of any kind or character, or create any obligation or indebtedness of the school district, except pursuant to section 18:7-60 of the title Education. Nor shall any action taken by the legal voters of the school district be effective in so far as it purports to raise by tax in any year any sum or sums for any purpose or purposes, except to provide for the payment of the interest on or principal of any debt or obligation of such school district or for the setting aside of necessary reserve or sinking funds therefor, in excess of the sum or sums voted to be raised by tax for like purposes in the preceding year without like assent of the commission.