The Board, in consultation with the Department of Treasury, shall establish loan interest rates that are benchmarked to a market index on an annual basis, not to exceed two percent per year for the localities with a school division composite index of local ability-to-pay between 0.0 and 0.299. The Board shall utilize a sliding scale based on the local school division’s composite index of local ability-to-pay to determine the interest rate on each such loan. Every loan made under the provisions of this chapter by selling the bonds, notes, or other evidences of debt of school boards for investment of the trust funds of the Virginia Retirement System shall bear interest at a rate not to exceed the maximum interest rate per year as established by the Board.