Every person employed in a teaching, supervisory or administrative capacity by the county or city board of education in the public schools of the state shall attend the institute held for the county or city in which such person is employed; provided, that the institute is held during the term-time or during the week immediately preceding the date of opening of the schools in the county or city. All persons attending such institute shall be paid as for time taught, and any person subject to institute attendance who fails to attend an institute called in accordance with the provisions of this chapter shall forfeit his or her contract with the respective county or city board of education as the case may be and shall be ineligible to employment in the public schools of the state for a period of six months from the date of such delinquency, unless excused as hereinafter provided.