Paragraph (2) of subsection (i) of section 89 of chapter 71, as so appearing, is hereby amended by striking out the first subparagraph and inserting in place thereof the following subparagraph:-

In any fiscal year, no public school district’s total charter school tuition payment to commonwealth charter schools shall exceed 9 per cent of the district’s net school spending; provided, however, that a public school district’s total charter tuition payment to commonwealth charter schools shall not exceed 18 per cent of the district’s net school spending if the school district qualifies under paragraph (3); provided further, that the commonwealth shall incur charter school tuition payments that exceed 9 per cent of a district’s net school spending if the school district qualifies under said paragraph (3). The commonwealth shall incur charter school tuition payments for siblings attending commonwealth charter schools to the extent that their attendance would otherwise cause the school district’s charter school tuition payments to exceed 9 per cent of the school district’s net school spending. The amount required to be paid by the commonwealth under this paragraph in any year shall not be reduced by a percentage greater than the percent reduction in chapter 70 funding.