Kindergarten (including pre-kindergarten programs) together with the first six grades shall constitute the elementary tenure area. In those schools in which instruction in the core academic subjects has not been departmentalized at the seventh and/or eighth grade levels, such grades shall constitute the middle grades tenure area. In those grades at or above seventh grade level in which instruction in the core academic subjects is departmentalized, the core academic subjects shall be grouped for tenure purposes into the academic tenure areas of English, social studies, mathematics, science and world languages.