BOSTON — A think tank is criticizing Gov. Charlie Baker's budget for increasing low-income student support at a lesser rate than other components of a major education funding reform law, prompting the administration to contend it actually boosted low-income aid more than the remaining categories.

In a new report, a Massachusetts Budget and Policy Center analyst wrote that the governor's fiscal year 2021 budget proposal (H 2) falls tens of millions of dollars short on low-income support in the first implementation year of the seven-year funding reform law.

While the annual spending bill delivers sufficient funding for most areas of need identified in the law, the organization wrote, it increases low-income student aid at a lower rate than other spending areas targeted in the so-called Student Opportunity Act.

"The goal of the Student Opportunity Act is to update our state funding for public schools so every child can get an excellent education, regardless of their background," MassBudget senior policy analyst and report author Colin Jones said in a statement. "Slower progress on any part of this new law means state lawmakers will have to play catch-up later. Meanwhile, schools would not be able to consistently phase in enhancements to their programs on schedule."

Baker's latest budget proposal calls for a $303.5 million bump in Chapter 70 funding the state pays to districts, more than twice the average annual increase between fiscal years 2013 and 2020 and more than one-seventh of the total $1.5 billion boost to be directed toward K-12 education under the law.

The law, which Baker signed in November, requires foundation budget and increment amounts to increase each year "in an equitable and consistent manner."

The report from the left-leaning MassBudget said most areas identified by the new law as needing investment — special education, health care, social-emotional support, and English language learner aid — would progress 14 percent, or one-seventh, of the way toward the seven-year goals outlined in the law under Baker's budget.

However, support for low-income students would only increase 4 percent under Baker's budget, leaving a bigger chunk to be made up in the remaining six years than other areas of reform, according to the report.

Increasing low-income aid to the same 14 percent level would raise the overall price tag another $74 million next fiscal year, the report found.

"Delaying extra funding for these youth cuts against the larger goal of the SOA and school finance system at large, to provide all kids, regardless of their background, the resources and support necessary to achieve academically and succeed," Jones wrote.

Baker's office disagreed with MassBudget's conclusion. According to the administration, low-income supports are broken into two components — low-income headcounts and per-student rates — that, when considered together, see a faster rate of increase than any of the other categories.

Any other increases to the low-income rates would require other areas of need to be cut or would force Chapter 70 increases to vary significantly by year, the administration said.

"The Baker-Polito Administration was pleased to work with the Legislature to sign the Student Opportunity Act into law, and has proposed an increase of over $300 million in additional state aid next fiscal year to school districts across the Commonwealth to fully fund the first year of the new law," Baker spokeswoman Anisha Chakrabarti said. "The Administration's budget proposal makes significant investments to support the education of low-income students, as outlined by the Legislature, while at the same time ensuring communities will see funding increases distributed evenly and consistently across the 7-year implementation timeline."

Sen. Sonia Chang-Diaz, a Boston Democrat who filed one of the underlying bills from which the final legislation was built, raised similar concerns as MassBudget about the administration's approach. While the overall funding increase is in "the right ballpark," she said the amount "is not distributed in an equitable way."

"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," Chang-Diaz said in a Jan. 22 statement. "When, oh when, are we going to stop putting poor kids at the back of the line?"

The budget proposal also moves the threshold for students to qualify as low-income to 185 percent of the federal poverty level, where it was before fiscal year 2017, rather than the 133 percent rate used in recent years.

Overall low-income enrollment will increase about 46,000 from fiscal 2020 to fiscal 2021, the Department of Education estimated. The administration also calls for a new methodology for counting low-income students beginning next year.

Both Chang-Diaz and MassBudget said the changing count alone does not justify what they see as insufficient funding for low-income student needs. Jones wrote in the report that the administration's plan "rests on questionable assumptions."

"This assumes that raising this threshold to count more children as low-income, counteracts the need to raise low-income rates at the same level as other portions of the formula," he wrote. "This defies the fact that both identification of low-income students and the adequate resources for each student are both necessary to deliver appropriate services."

The House and Senate in April and May will draft their own approaches to fiscal 2021 K-12 education funding.