(1) District school boards may hire certified and qualified personnel as provided in ss. 1012.39 and 1012.57 to teach a specified number of periods, which may be less than a full school day or less than a full school year.
(2) Assigned additional school duties and salaries shall be given in direct ratio to the number of periods taught. Other benefits shall be provided by district school board rule or, if applicable, pursuant to chapter 447.