An SAT score of 1300 or higher can open a path to America’s top public and private colleges. But new data, for the first time at this level of detail, shows that just a sliver of the country’s poorest students reach that level.

The children of the richest 1% are 13 times as likely as the poorest students to score that high. More than one-quarter of them do, compared with 5% of middle-class students — demonstrating how much students’ standardized test scores rise with parents’ incomes, and how disparities start years before students sit for tests.

The researchers, economists at Opportunity Insights, based at Harvard University, matched all students’ SAT and ACT scores for 2011, 2013 and 2015 with their parents’ federal income tax records for the prior six years. Their analysis, which also included admissions and attendance records, found that children from very rich families are overrepresented at elite colleges for many reasons, including that admissions offices give them preference.

But the test score data highlights a more fundamental reason: When it comes to the types of achievement colleges assess, the children of the rich are simply better prepared.

The disparity highlights the inequality at the heart of American education: Starting very early, children from rich and poor families receive vastly different educations, in and out of school, driven by differences in the amount of money and time their parents are able to invest. And in the past five decades, as the country has become more unequal by income, the gap in children’s academic achievement, as measured by test scores throughout schooling, has widened.

“Kids in disadvantaged neighborhoods end up behind the starting line even when they get to kindergarten,” said Sean Reardon, the professor of poverty and inequality in education at the Stanford Graduate School of Education.

“On average,” he added, “our schools aren’t very good at undoing that damage.”

In the wake of the Supreme Court decision ending race-based affirmative action, there is political momentum to address the ways in which many colleges favor the children of rich and white families, such as legacy admissions, preferences for private school students, athletic recruitment in certain sports and standardized tests.

Yet these things reflect the difference in children’s opportunities long before they apply for college, Reardon said. To address the deeper inequality in education, he said, “it’s 18 years too late.”

Heightened Competition

The children of the top 0.1%, whose parents earned an average of $11.3 million a year in today’s dollars, got far better scores than even the children of the families just below them, the new data shows. For the 12,000 students in this group, opportunities that drive achievement were amplified — exclusive private schools, summers traveling the world and college prep services that cost more than college itself — said John N. Friedman, an economist at Brown, who analyzed the new data with Raj Chetty and David J. Deming of Harvard.

But the larger inequality is between the children of the merely rich and those below them. Relatively few poor children take the test at all.

As class differences have grown more extreme and a college degree has become more crucial to achieving a middle-class lifestyle or better, competition among parents anxious about their children’s futures has risen.

“People are kind of jockeying to get into the school district that they think is going to be most beneficial for their kid,” said Ann Owens, a professor of sociology at the University of Southern California, who studies inequality in education. “A lot of this is driven by rising income inequality. When people have more money to spend on stuff, they’re spending it on moving to an affluent neighborhood, or buying their kids test prep and tutors and all these things they think will help them.”

Unequal Neighborhoods

Research shows that the more funding schools get, the better students do. Instead of schools being financed with varying amounts of money based on property taxes, most states now spend the same amount per student, or more for students in low-income schools. The bigger disparities are now among states.

But as differences in school funding have shrunk, differences in other resources in children’s lives have grown. Children are increasingly likely to live and attend schools in neighborhoods of concentrated poverty or affluence. Since the mid-1990s, neighborhoods have become more segregated by income — but only for families raising children, Owens found. As school districts become more segregated, achievement gaps grow larger, she found.

Schools in poor neighborhoods have been shown to have a harder time attracting and retaining the best teachers. Also, these schools’ financial needs are greater — they may need to spend money on getting students to grade level or repairing buildings, while richer schools can spend it on things such as arts teachers or field trips.

Rich parents are more likely to have the time and connections to be highly involved in their schools — volunteering in classrooms, lobbying on behalf of the school and raising money through school foundations.

The goals and experiences of the people in their neighborhood rub off on children, too. Friendships that cut across class have a bigger effect on children’s outcomes than school quality, previous research by Chetty and colleagues found. Segregated neighborhoods make these friendships harder to find.

Differences in academic performance by race have shrunk in the past 50 years, Reardon has shown. But Black and Hispanic families are disproportionately likely to live in poor neighborhoods, even compared with white families who earn similar incomes, and their children are more likely to attend high-poverty schools.

“Black, Hispanic, Native American kids attend lower-income schools,” Owens said. “It’s not that sitting next to a white kid is magical. It’s money in schools.”

‘Shadow Education’

The differences among schools are less important than what happens outside of school, a variety of research suggests — what children do at night and on summer breaks, their parents’ vocabularies, and the level of stress in their home lives. Although the heritability of cognitive ability appears to play some role on an individual level, there is also a lot of evidence that environment matters.

“K-12 schools only manage 10% of children’s time, and they do it pretty equitably,” said Nate G. Hilger, the author of “The Parent Trap: How to Stop Overloading Parents and Fix Our Inequality Crisis” and an economist. “The other 90% of nonschool time — early childhood, after school, summer, private extracurriculars, counseling, tutoring, coaching, therapy, health management — masks all the most important inequality of opportunity.”

It starts early: High-income children are more likely to have attended preschool. Before kindergarten, the average cognitive scores for the children of the highest-earning families are 60% above the scores of the lowest earners. The early advantage continues: Children who attend high-quality preschools have been shown to have higher chances of taking the SAT and going to college.

Parents have embraced what researchers call intensive parenting — the idea that parents should immerse children in continual learning. Half a century ago, rich and poor parents spent about the same amount of time with their children. Now high-income parents spend more one-on-one time with them on activities such as reading — what Robert Putnam, the political scientist who wrote “Our Kids: The American Dream in Crisis,” calls “‘Goodnight Moon’ time.”

The share of money rich parents spend on their children is also increasing — especially in places where inequality is worse. Test prep for the SATs is just one example of what researchers call “shadow education.” Throughout children’s lives, parents who can afford it pay for extracurricular and cultural activities to enrich their children outside school.

Poor families have more stressors, such as food insecurity and frequent moves, that have been shown to have long-term effects on children’s academic performance. They also affect parents.

“Parents, regardless of race, nationality, income, they have big dreams for their kids, they want them to do well in school,” Reardon said. “But if you’re worried about whether there’s food on the table and the heat’s on in winter, it’s very hard to make sure you set aside an hour before bedtime to read to your kids.”

Closing the Gap

By the time rich children take the SAT, researchers speculate, experiences such as bedtime reading, museum visits and science summer camps may contribute to their scores. “They’ve gone to better schools, they’ve read more novels, they’ve learned more math,” said Jesse Rothstein, a professor of public policy and economics at the University of California, Berkeley.

If the SAT is, in a sense, a wealth test, education research suggests that is a symptom of the problem, not the cause. Other parts of college applications, such as essays and letters of recommendation, are also influenced by socioeconomic background. And data suggests that children with high SAT scores are more prepared for demanding college coursework, and more likely to have high earnings or prestigious jobs in adulthood.

The solution, researchers say, is addressing achievement gaps much earlier, through things such as universal pre-K, increased funding for schools in low-income neighborhoods, and reduced residential segregation.

It could benefit all parents and students, even wealthier ones. Parenting in highly unequal societies is intense and competitive, driven by fear of the increasing risk that children will be worse off than their parents. Parenting in places with less income inequality and more public investment in families is more playful and relaxed, research shows. When the risk of falling is smaller, a college admissions test becomes less fraught.

This article originally appeared in The New York Times.