In the roiling national debate about the best ways to improve public education, one aspect gets scant attention: the relationship between the tax dollars school systems spend and academic results.

In a report released Wednesday, the left-leaning Center for American Progress looks at how much “bang for the buck” taxpayers are getting from public schools.

Ulrich Boser, who wrote the report, analyzed budgets of 7,000 school districts across about 40 states — which enroll about about 80 percent of U.S. public school students — and found some surprising results.

Relatively affluent school districts in communities such as Montgomery County, Md., or Scarsdale , N.Y., spent a lot on each student ($15,421 in Montgomery and $24,607 in Scarsdale) and posted strong academic results, but other districts in their states got similar academic results with less money.

“We think of these districts as being careful with their money but they must also have productivity issues,” Boser said in an interview.

Below is an interactive tool from the Center for American Progress that shows the productivity ranking for school districts in nearly 40 states. Use the pull-down menu to select a state and scroll through the rankings by school district.

Schools in high-poverty neighborhoods are more than twice as likely to be among the least-productive school districts, according to the report, even when adjustments are made for the higher cost of educating low-income students as well as those with special needs or English language learners.

Hispanic students are twice as likely to attend schools in the least-productive districts than the most-productive districts, while black students are eight times more likely to be in the least-productive districts than in the most-productive districts, according to the study.

School districts often spend money on items that might do nothing to improve student achievement, Boser found. For example, many school districts pay a premium to teachers with master’s degrees, even though there is no evidence that advanced degrees translate into better student test scores. According to one 2009 study, the country spends about $15 billion a year paying out “master’s bumps” to teachers.

That doesn’t mean the U.S. should cut funding for public education, Boser said. Rather, school districts and states should spend more strategically, he said. The nation spends about $600 billion a year on K-12 public schools.

Boser created a Return on Investment index by rating school districts on how much academic achievement they attained for every dollar spent, relative to other districts in their state.

Academic achievement was measured using state reading and math tests in elementary, middle and high school. The data used were from 2010-2011 school year.

The analysis did not include thousands of small school districts in sparsely populated states that did not have enough districts to make comparisons within states. Excluded were Alaska, the District of Columbia, Hawaii, Kansas, Maine, Montana, Nebraska, New Hampshire, North Dakota, Oklahoma, South Dakota and Vermont.

States and school districts have reams of financial data and, as a result of the federal No Child Left Behind law, also collect mountains of academic data.

“In one side of the district office, they’re talking about achievement and on the other side of the office, they’re talking about spending,” Boser said. “What we need to do is to have a national conversation that looks at both of these, so that we can make the smartest decisions about the best way to spend money.”

Just two states, Florida and Texas, routinely examine productivity in school spending, Boser found.

And a few others are taking steps in the right direction, the report said.

Virginia analyzes school district budgets to find savings outside the classroom that can be used for instruction. The state sends consultants to review a district’s financial data, a cost that is split between the state and the district. In 2012, consultants examined Arlington Public Schools and made a raft of recommendations, from reorganizing the way custodial supplies were purchased to trying to entice more students to buy school lunches. The state estimates that since 2003, more than 30 school districts have undergone reviews and saved approximately $40 million.