A state senator who has advocated for education funding reform is pushing back against Gov. Charlie Baker's description of his fiscal 2021 budget proposal as "fully" funding the new school finance law.

In keeping with the law Baker signed in November, the $44.6 billion budget he filed Wednesday recommended a $303.5 million increase in Chapter 70 aid to local schools. Baker said his budget "will fully fund the first year of the Student Opportunity Act," which committed the state in $1.5 billion in new funding for K-12 education over seven years.

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Sen. Sonia Chang-Diaz, a Democrat who filed one of the bills on which the Student Opportunity Act was based, said Baker's budget does not fully fund "both the letter and spirit of the Student Opportunity Act." She said its overall Chapter 70 number "is in the right ballpark," but the total "is not distributed in an equitable way across the four categories" specified in the law.

Pointing to information from the Department of Elementary and Secondary Education, Chang-Diaz said Baker's plan "takes a 14% step toward full implementation" for health care, special education and English learners, but a 4 percent step for low-income students.

"The Baker Administration justifies this disparity by saying that they're putting other money toward low-income students by accurately counting how many of them are poor. Great," Chang-Diaz said in a statement. "But paying for the accurate head-count of low-income kids does not give the Governor, or the Legislature, a 'hall pass' from also paying to adequately educate them. For the past three years, upper-income communities' interests have been front-loaded, with the prioritization of the health-care rate and 'effort reduction' aid. When, oh when, are we going to stop putting poor kids at the back of the line?"