1. Except as otherwise provided in this section, each student shall enroll in at least four units of high school work in each grade from nine through twelve.

2. A student in grade twelve may enroll in fewer than four units of work, provided: a. The student requires fewer than four units of work for graduation; and b. The board of the school district has adopted an alternative high school senior curriculum plan.

3. An alternative high school senior curriculum plan becomes effective if: a. It is adopted by action of the school board; b. It contains specific criteria under which a high school senior may enroll in fewer than four units of work; and c. It has been submitted to and approved by the superintendent of public instruction.