Instead, schools must adapt to the new low-income majorities, Suitts said.
"We have an education system that continues to assume that most of our students are middle-class and have independent resources outside the schools in order to support their education," Suitts said. "The trends and facts belie that assumption. We can't continue to educate kids on an assumption that is 20 years out of date. We simply have to reshape our educational system."
Policymakers, politicians and educators should reconsider the $500 billion the nation spends annually on K-12 education, with an eye toward smarter investments to help poor children, Suitts said.
Because they show up for kindergarten with a working vocabulary half as large as their more privileged peers, low-income children should be enrolled in quality preschool, Suitts said. Poor children also need more time in school with an extended day or school year, and they need health care as well as social and emotional support, he said.
"We have to do something different by the way we educate, but we do it by understanding who are the students and what are the needs," Suitts said.
On average, the country spends about $10,300 annually per student, but that figure varies wildly among states and even within school districts. In 2011, for instance, New York spent $9,076 for each student, while Utah spent $6,212.
Between 2000 and 2010, average per-pupil spending increased, but more slowly than the growth in low-income students in every region but the Northeast, where per-pupil spending grew faster, the study found.
All three levels of government — federal, state and local — pay for public schools. The federal contribution is about 10 percent, with states and local governments providing the rest.
Because local governments draw on property taxes to provide their share of school funding, poor districts with a limited tax base don't raise as much money as more affluent communities. That often means that children in poor communities attend schools with fewer resources, substandard facilities and less-qualified teachers.