The school committee shall do all purchasing pertaining to the public schools and shall maintain records of receipts and expenditures in such manner as shall be required by the state and by the department of finance of the town. Records shall at all times be available showing receipts, expenditures and encumbrances upon unexpended appropriations. Expenditures of funds allocated to the public schools shall be made only by authorized vouchers signed by the superintendent of schools, and the chairman or clerk or such member of the school committee as may be designated by the school committee for that specific purpose. All purchases shall conform with town ordinances for bidding and awarding contracts unless the school committee determines that the purchase at bid is not practicable or consistent with its educational policy. (Amended, November 4, 2008.)