Section 59. The school committee of a town not in a superintendency union or district shall employ a superintendent of schools and fix his compensation. A superintendent employed under this section or section sixty or sixty-three shall manage the system in a fashion consistent with state law and the policy determinations of that school committee. Upon the recommendation of the superintendent, the school committee may also establish and appoint positions of assistant or associate superintendents, who shall report to the superintendent, and the school committee shall fix the compensation paid to such assistant or associate superintendents. The school committee shall approve or disapprove the hiring of said positions. Such approval by the school committee of the recommendation shall not be unreasonably withheld; provided, however, that upon the request of the superintendent the school committee shall provide an explanation of disapproval.