(a) Any school district may, by resolution of its board, operate one or more schools within the district on a full year school plan approved by the State Board of Education. Any board which operates under this subsection (a) shall devise a plan so that a student’s required attendance in school shall be for a minimum term of 180 days of actual attendance, including not more than 4 institute days, during a 12 month period, but shall not exceed 185 days. Under such plan, no teacher shall be required to teach more than 185 days. A calendar of 180 days may be established with the approval of the State Board of Education.
     (b) Any school board that operates one or more schools within the school district on a pilot full-year school plan under subsection (a-5) of Section 2-3.25f of this Code shall devise a plan so that a student’s required attendance in school shall be for a minimum term of 215 days of actual attendance, including not more than 4 institute days, during a 12-month period. A calendar of 215 days may be established with the approval of the State Board of Education.