If compensation is provided to certificated employees of any elementary, high, or unified school district for a work assignment which is not part of the contracted instructional day duties, like compensation, whether paid on an hourly or monthly basis, or on a flat rate basis or otherwise, shall be paid to all certificated employees of the district who perform like work with comparable responsibilities. Under no condition shall certificated employees who are working comparable hours and responsibilities beyond the instructional day be paid differently based on the employee’s sex. Nothing in this section shall be construed as prohibiting a school district from establishing a salary schedule based on experience for persons who are employed for such work. Nothing in this section shall be construed as requiring a district to compensate certificated employees for work assignments which are not part of the contracted instructional day duties simply because other employees of the district receive compensation for work assignments which involve different types of service.