The department of elementary and secondary education shall, by July 1, 2015, develop a high school graduation policy that allows a student to fulfill one unit of academic credit with a district-approved agriculture or career and technical education course for any communication arts, mathematics, science, or social studies unit required for high school graduation in any combination up to fulfilling one requirement in each of the four subject areas. The substitution may not be made where the course for which the agriculture or career and technical education course is being substituted requires an end-of-course statewide assessment. The credit cannot be substituted for any course which requires a statewide end-of-course assessment. The policy required under this section shall be in addition to the optional waiver of one unit of academic credit for a three-unit career and technical program of studies.