Section 11. If in any fiscal year a district’s actual expenditure for public education is less than the amount required to be appropriated for public education pursuant to this chapter, the difference, up to 5 per cent of the amount required to be appropriated, shall be spent for public education in the following fiscal year; provided, however, that any unexpended funds, whether appropriated to the school committee account or to town accounts for expenditure to meet public education costs, shall be deemed reappropriated for public education in the following year without further action by the appropriating authority; provided, further, that the amount of state school aid for the following fiscal year shall be reduced by the amount said difference exceeds 5 per cent of the amount required to be appropriated; and provided, further, that in any year in which additional money is required to be spent due to a spending deficiency in the prior year, if a district fails to spend the carried forward amount or under-spends its current year budget by more than 5 per cent of the amount required to be appropriated for that year, state school aid in the following year shall be reduced by the entire difference between those amounts. The board shall promulgate regulations to enforce the provisions of this section.