The public school districts of the state, in their discretion, may pay with local funds one hundred percent (100%) of the cost of the health insurance premiums of the State and School Employees Health Insurance Plan for all retired members of the Public Employees’ Retirement System who are employed as school bus drivers by the school districts. No state funds shall be used for payment of the health insurance premiums under the authority of this section. If a school district chooses to pay the health insurance premiums for school bus drivers under the authority of this section, the district shall be authorized to pay any amount that is one hundred percent (100%) or less of the cost of the health insurance premiums for the school bus drivers.