The commissioner shall make a regional adjustment in the total operating allocation for each school administrative unit determined pursuant to section 15683. The regional adjustment must be based on the regional differences in teacher salary costs, for labor market areas in which the school administrative unit is located, as computed by a statewide education policy research institute, and must be applied only to appropriate teacher salary and benefits costs as calculated under section 15678 and salary and benefit costs of other school-level staff who are not teachers as calculated under section 15679. Beginning in fiscal year 2012-13, and for each subsequent fiscal year, the commissioner shall make a regional adjustment in the total operating allocation for each school administrative unit determined pursuant to section 15683. The regional adjustment must be based on the regional differences in teacher salary costs, for labor market areas in which the school administrative unit is located, as computed by a statewide education policy research institute, and must be applied only to appropriate teacher salary costs as calculated under section 15678 and salary costs of other school-level staff who are not teachers as calculated under section 15679.   [PL 2011, c. 419, §2 (AMD).]