Not only are more American children poor today than before the Great Recession, but poor kids are increasingly clustered with poor classmates at school, according to an analysis from the nonprofit EdBuild.

Between 2006 and 2013, the number of students in high-poverty school districts — in which more than 20 percent of children live below the federal poverty line — increased from 15.9 million to 24 million, according to EdBuild. That means nearly half of the nation’s 50 million public school students go to class with large numbers of peers who are growing up with poverty and all its difficulties.

The number of children going to class in school districts with even greater student poverty — higher than 40 percent — also increased, from about 1 percent to 4 percent of the national student population.

Such high-poverty districts need more money to help address the issues that their students bring to school, including hunger, homelessness and higher risks for mental health challenges, said Rebecca Sibilia, founder and CEO of EdBuild, a new group that advocates for more equitable school funding systems.

“What we’re seeing is a huge spreading of poverty, but potentially more problematic is a deepening of poverty,” said Sibilia, who has worked at StudentsFirst, the lobbying group founded by former D.C. school chancellor Michelle Rhee. “The needs of high-poverty districts are just compounded compared to a smattering of low-income students that may exist in middle-income areas.”

EdBuild produced an interactive map that shows how poverty levels have changed in each of the nation’s 14,000 school districts. Here’s what poverty levels looked like in 2006:

And in 2013:

As the map makes clear, the Midwest and the South have experienced the most dramatic increase in student poverty. The South enrolls about 35 percent of the nation’s students but accounts for 60 percent of all students living below the federal poverty line, according to Sibilia.

Nowhere has there been a more significant change than in Florida.

In 2006, 6 percent of Florida students went to school in high-poverty districts. By 2013, 76 percent of the state’s school-age children were living in high-poverty districts, according to EdBuild.

There are plenty of examples of hard-hit communities outside the South and Midwest. Take New Mexico, a state that had plenty of struggling families before the recession — nearly half of its students were living in poverty. Now that’s up to 87 percent, making New Mexico second only to Mississippi nationwide, according to EdBuild.

In Florida, New Mexico and elsewhere, the rise in student poverty has shown up in many kinds of communities, including suburban and rural ones. What many of those diverse high-poverty school districts have in common, however, is trouble raising as much money for education as their more affluent counterparts.

As a result, schools with the most poverty and greatest needs often have less to spend per student than schools in wealthier communities. Nationally, nearly half the states spend less on students in their poorest schools than in their richest schools.

“That’s kind of upside down,” Sibilia said.

EdBuild wants to see the neediest schools get more money to serve their students. And that means moving away from the heavy reliance on local property taxes that characterizes school funding systems in most places, and that inevitably leaves poor communities with less to spend on education, Sibilia said.

“The state really needs to step up and own their role in being the majority funder for schools,” she said.

EdBuild’s interactive map is here.