Sections 124D.12 to 124D.127 authorize districts to evaluate, plan and employ the use of flexible learning year programs. It is anticipated that the open selection of the type of flexible learning year operation from a variety of alternatives will allow each district seeking to utilize this concept to suitably fulfill the educational needs of its pupils. These alternatives must include, but not be limited to, various 45-15 plans, four-quarter plans, quinmester plans, extended learning year plans, and flexible all-year plans. A school district with an approved four-day week plan in the 2014-2015 school year may continue under a four-day week plan through the end of the 2019-2020 school year. Future approvals are contingent upon meeting the school district's performance goals established in the district's plan under section 120B.11. The commissioner must give a school district one school year's notice before revoking approval of its flexible learning year program.