A school district located in whole or in part within a city having a population of twenty-five thousand one hundred or more may establish a pension and annuity retirement system for the public school teachers of such district. However, in cities having a population less than seventy-five thousand, establishment of the system shall be ratified by a vote of the people at a regular school election. [C24, 27, 31, 35, 39, § 4345; C46, 50, 54, 58, 62, 66, 71, 73, 75, 77, 79, 81, §294.8 ] 2009 Acts, ch 57, §79 Referred to in §294.11 , 294.12