For purposes of sections 79-875 to 79-878, student teacher or intern means a student who is enrolled in a postsecondary educational institution approved by the State Board of Education for teacher training and who is jointly assigned by such institution and a board of education to student-teach or intern under the direction of a regularly employed certificated teacher, principal, or other administrator. Student teaching may include duties granted to a certificated teacher under the rules and regulations of such board and any other part of the school program for which either the cooperating teacher or the principal is responsible.