The report set out to answer how this overhaul affected student performance in school districts that had spent the least per student on education before the state began its effort compared with those that spent the most. The lowest spenders were mostly small, outlying suburbs, rural towns, and a few cities, such as Lawrence and Springfield, while the biggest spenders were generally wealthy suburbs and a few cities, such as Boston.

The Education Reform Act established a new system for funding local schools, based on a formula that took into account - among other things - student demographics and per-student spending at that time. It also created a set of statewide academic standards and the Massachusetts Comprehensive Assessment System tests to assess whether these goals are being met.

"Whether increases in state aid are enough to adjust the cost of serving these students we don't know," said one of the report's authors, Thomas Downes, an associate professor of economics at Tufts University. "I think the difficulty these districts face is going up and up and up."

Yet the extra cash delivered under the education bill did little to narrow the achievement gap between high- and low-spending districts because test scores often increased at similar rates. The report also warned that much work remains in wiping away, or at least chipping away, at the gaps in performance that persist among students of different demographic backgrounds, especially among low-income students and nonnative English speakers.

This cautionary note looms large over the otherwise significant gains achieved over the past 15 years, including steady improvement on state and national standardized tests and increased equity among school districts on per-pupil spending. In fact, had the state not infused millions of dollars into public schools and adopted rigorous academic standards, the achievement gap between low- and high-spending districts would have widened considerably, said the report, funded by Bank of America .

The changing demographics call into question the likelihood of the state meeting the bold vision of its overhaul effort: that all students, regardless of their ZIP code, can achieve at their highest levels, according to the report, "Incomplete Grade: Massachusetts Education Reform at 15" by MassINC., a nonpartisan public policy research and educational institute.

Those findings pale in comparison to a 272 percent increase in low-income students in Randolph, where years of Draconian budget cuts have prompted middle-class families to shun the school system, causing the percentage of low-income students to swell to 43.1 percent.

In Brockton and Everett, the percentage of low-income students during that period more than doubled to well above 50 percent, while in Revere, it nearly doubled to 62.3 percent.

Surging levels of poverty and immigration present some of the most serious obstacles to boosting student achievement, according to a new report being released today that examines the first 15 years of the state's 1993 Education Reform Act.

To predict what may have happened had the state not overhauled public education, researchers examined test scores for fourth- and eighth-graders in math and English under the old state testing system, starting in 1988, and then projected out test performance based on those scores after the exam was phased out in the mid-1990s. That data predicted that the lowest spenders would have experienced a marked decline in performance while top spenders' performance would have risen.

They then compared those results to how the districts actually did under MCAS, which premiered in 1998 and is based on statewide academic standards for every grade level that were created under the reform law. Both groups largely experienced increases.

Researchers do not know for certain what is causing some school districts to experience changing demographics, but they suspect that middle-class flight from some districts and the settlement of new immigrant families, many of whom are struggling to make ends meet, are significant factors. In many cases, the affected school districts, mostly urban centers with reasonably priced housing, are seeing simultaneous increases in low-income students and nonnative speakers of English.

Paul Reville, the state's education secretary, said Massachusetts has done well in holding schools accountable for test results, but now needs to devote more attention to developing programs to help academically struggling students.

"Our achievement gaps are quite wide and have not closed appreciably," said Reville, noting that Governor Deval Patrick's 10-year overhaul of public education aims to shrink the gaps.

Finding money could be difficult, however, because the state's economy appears to be in a tailspin, said the report. As it is, many districts have not fully recovered from staffing and program cuts earlier this decade when a milder recession prompted state officials to reduce school aid.

Everett confronts the challenges daily. In addition to high levels of poverty, more than 40 percent of students do not speak English as their first language and nearly 10 percent of students speak only limited English.

"Many immigrant families don't have the resources other families have to buy their youngsters books to read or take youngsters to historical sites that are so abundant in our area," said Thomas Stella, the school system's assistant superintendent. "They don't have the same opportunities. As a result they play catch up for a good portion of the school year."

Richard Silverman, Randolph school superintendent, said the state funding mechanism created under the Education Reform Act does not adequately address the complex problems faced by the poorest school districts.

"The current formula, as progressive as it tried to be, isn't sufficient," Silverman said. "Few if any social service agencies are serving Randolph. . . . Much support for kids and families has to come through the schools. Randolph is trying to do that but needs additional help."

James Vaznis can be reached at jvaznis@globe.com.

© Copyright 2009 Globe Newspaper Company.