While scrolling through Instagram, Joi Mitchell saw an ad for Saga Education, a nonprofit that provides high-impact tutoring in schools, and clicked on it.

“I was running away from teaching because my whole family are teachers,” she said. “But I always wanted to work with kids.”

She signed on and started tutoring students at two Washington, D.C., public high schools last year. At first, it was heavy lifting. With one student especially, she said, it felt “like I was falling on a brick wall — he was always trying to ditch Saga.” So she spoke to him one-on-one, explaining how tutoring could help him. He began showing up and making progress.

“The most fulfilling part of tutoring is that ‘aha’ moment when students finally believe in themselves, too,” Ms. Mitchell said. “My mom calls it the teacher drug.”

The most recent National Assessment of Educational Progress (NAEP) scores — often called the nation’s report card — came out on Sept. 1 and the results were not just a wake-up call, but a fire alarm. The test, taken by 9-year-olds nationwide, showed math scores plunging by seven points from prepandemic levels, and reading scores by five, erasing roughly two decades of academic progress.

As schools confront this massive learning loss, in-school tutoring may be one of the most effective tools they have to get students back on track, many experts said. The federal government is confident enough about the evidence behind tutoring that it is investing heavily in such programs.

While tutoring during Covid conjures reports of teachers hired away to lead private pandemic pods, or families with means paying generously for tutoring outside school, the kind of tutoring Ms. Mitchell did — high-dosage, in-school learning in small groups — is one of the most powerful interventions the public education system has, with a large body of research showing benefits like higher graduation rates, reduced absenteeism and the ability to close half a year’s gap in learning.

Research out of the University of Chicago on Saga Education’s model shows an even greater potential impact: the ability to close a gap of up to two and a half years of math in a single school year.

In April, the U.S. Education Department announced over $220 million of funding — $160 million in federal grants from the American Rescue Plan, along with additional funding from philanthropic sources — to help districts build evidence-based tutoring and enrichment programs to assist with academic recovery. This is in addition to the $122 billion in rescue plan funding, passed in March 2021, which was already allocated for school support over three years.

The national report card results “show the historic disruption in schooling the president has been sounding the alarm on,” said Maureen Tracey-Mooney, special assistant to the president for education policy. The American Rescue Plan funding, she said, is a multiyear response to that. Research out of Georgetown University suggests that many districts are already spending some of the $122 billion on tutoring.

The biggest challenge to implementing these programs, of course, is cost. In-person tutoring is expensive, requiring close coordination with the classroom and a large supply of tutors. But advocates argue that it’s worth the effort.

Matthew Kraft, an associate professor of education and economics at Brown University and a co-author of a paper on how to build a national tutoring program, said that, in more than a decade of research, he has yet to see a body of evidence “as broad and compelling as the evidence for high cost, intensive long-term tutoring” in public schools. He estimates the cost of universal K-12 public school tutoring at about $50 billion a year.

Still, while the current rescue plan funding is not enough to support every public school student experiencing learning loss — “and that’s a hard truth to swallow,” Dr. Kraft said — the initiative presents a real opportunity to help students.

As long as it’s done right.

Alan Safran, chief executive and co-founder of Saga Education, which has provided tutoring guidance to the Education Department and is Ms. Mitchell’s employer, explained that high-impact tutoring “has to be built into the school day, not as an after-school afterthought.” In addition, students need to meet consistently with the same trained tutor, in groups of two or three, two to three times a week.

Since 2018, the Bill & Melinda Gates Foundation — one of the philanthropic investors providing funding for in-school tutoring — has worked with Saga to significantly bring down the cost of in-person tutoring, to $1,300 per pupil from $3,400 per pupil. That accomplishment represents the kind of innovation the new funding is designed to support. Bob Hughes, the director of K-12 Education for the foundation, said he hopes that, through research, schools can eventually understand which students need a $500 tutoring model, versus $1,200 or $3,400, making these programs more sustainable with public dollars.

Mr. Safran believes a national tutoring program would be effective if schools focus most aggressively on third grade literacy and algebra, as research shows students who are at grade level in these subjects are four times as likely to graduate high school. He puts the price tag at $3 billion a year and said — between federal Title 1 funding for highest-need students and the American Rescue Plan — he believes it’s possible.

“The most important thing is not to spread the money too thin,” said Nate Hilger, author of “The Parent Trap” and an economist who focuses on family policy.

With a whole cottage industry of for-profit tutoring and ed tech start-ups emerging, many without research to back them up, accountability will be vital.

“We’ve got really strong evidence for in-person models that work but are hard to scale,” said Kevin Huffman, the former commissioner of education for Tennessee and now chief executive of Accelerate, a $65 million initiative, which aims to cultivate and scale high-impact tutoring models. “Then there are people trying all kinds of things that are not that, with limited evidence.”

The Education Department will be tracking programs for their effectiveness through its School Pulse Panel survey, with the specific goal that students close a four-month gap in learning.

One of the most urgent, and potentially transformative, areas for research is online tutoring, which could greatly expand the pool of trained tutors available to schools. First, though, it would have to overcome the wariness left by Zoom school among many parents and districts.

At Uplift Gradus Preparatory, a public charter school in DeSoto, Texas, Trish Cook saw her fourth-grade students make significant strides in math last year, with the online tutoring program Intervene K-12. “These were trained tutors — it was clear they had some educational and leadership background, and they were able to get those kids in order. Morale went up.” Part of this is because students felt more comfortable asking questions in small groups than in front of the whole class, Ms. Cook noted.

Damir Hill, a sophomore at Ron Brown High School in Washington, D.C., thrived in a smaller group setting with his Saga tutor last year, though he was skeptical at first.

“I heard it was a math class, so I thought I would fail. Math was not really my strong suit,” he said. “But my tutor made math way more fun for me.” Last spring, Damir was named Saga Superstar of the month; he celebrated with a victory lap around the hall.