Kindergarten student Ronny Vaca (center) raises his hand in music class at Guilford Elementary School, a Title I high-poverty school in Loudoun County, Va., one of the nation’s wealthiest counties. (Photo by Evelyn Hockstein/For The Washington Post)

Low-income kindergartners are entering school with stronger math and reading skills, narrowing the academic gap with their affluent peers and reversing a decades-old trend, according to research released Friday.

The good news surprised researchers, who had expected to see school-readiness gaps growing — particularly given the broad societal trends of increasing income inequality and economic segregation.

“It’s not like the lives of the rich and the poor have gotten more equal, so we thought the trend of the widening gap would continue,” said Sean Reardon, a Stanford University professor of poverty and inequality in education. He co-authored the study with Ximena Portilla of MDRC, and it was published Friday in AERA Open, a peer-reviewed journal of the American Educational Research Association.

Reardon had previously found that academic achievement gaps grew substantially from the 1970s to 1990s. But he and Portilla found that between 1998 and 2010, academic gaps between low-income and high-income kindergartners shrank between 10 percent and 16 percent. That’s a significant change, but the gap remains large: At the current rate of improvement, it would take between 60 years and 110 years to do away with it.

The gap between white and Hispanic kindergartners narrowed 14 percent, and the gap between white and black kindergartners appeared to narrow somewhat, but the margin of error was too large to say for sure.

The data came from two large-scale surveys in which researchers spoke to teachers about students’ abilities and administered one-on-one assessments that measured skills such as letter and word recognition, rhyming sounds and vocabulary, as well as problem solving and familiarity with numbers, shapes and patterns.

So what explains the narrowing gaps?

It might be that the nation’s increasing focus on and investments in early childhood education have given more low-income children a chance to go to preschool, Reardon said. But the data on that are conflicting and inconclusive, he said.

What does seem clear is that low-income parents are spending more time reading with their children and taking them to enriching places like museums, zoos and libraries. Low-income families also have more books and computers at home than they once did — closing a different kind of gap with affluent families, according to a separate study also published Friday in AERA Open and written by Reardon and several other scholars.

“The big increases in those kinds of activities aren’t coming among high-income families, who were already doing them a lot, but among low-income families. So there’s this growing parity … and we know these things are important for school readiness,” Reardon said. “There’s still a disparity, but it’s not as big as in the past.”

He said it seems that public information campaigns about the malleability of young minds and the importance of early literacy are succeeding in helping low-income families understand what they can do at home to prepare their children for school.

But Reardon cautioned that individual parents’ investments of time, energy and money are never going to close the substantial gaps that separate poor and rich kids when they enter kindergarten — and that then persist, leading to enormous achievement gaps throughout elementary school, middle school and high school.

That’s going to take structural changes that attack root problems like income inequality and segregated neighborhoods, he said: “It’s not like we just keep reading to our kids and it’s all going to go away.”