Teachers working less than thirty hours a week, but no less than fifteen hours a week, shall qualify for state health and dental insurance. The Public Employee Benefit Authority is directed to amend its "Plan of Benefits" regarding fringe benefits to conform to the provisions of this section. Teachers and employers shall each contribute toward the cost of these benefits with the employer paying only that portion of the employer’s normal cost which is attributable to the time the teacher is working, and the teacher shall pay all remaining costs. However, the employer’s contribution shall be no less than half the normal cost.