certification of returns.] One of the judges shall be chairman of the election board. Before entering upon the discharge of their duties election judges shall take an oath for the faithful performance of their duties as such in the manner prescribed by the general election laws of the state.

The polls shall be opened at nine o’clock in the morning of the day fixed for any such election and shall be kept open until six o’clock p.m. of the same day. Immediately following the closing of the polls the clerk of the board of election shall forthwith transmit the returns duly certified by the election judges to the secretary of the board of directors of the district.