In the thick of the Covid-19 pandemic, Congress sent $190 billion in aid to schools, stipulating that 20 percent of the funds had to be used for reversing learning setbacks. At the time, educators knew that the impact on how children learn would be significant, but the extent was not yet known.

The evidence is now in, and it is startling. The school closures that took 50 million children out of classrooms at the start of the pandemic may prove to be the most damaging disruption in the history of American education. It also set student progress in math and reading back by two decades and widened the achievement gap that separates poor and wealthy children.

These learning losses will remain unaddressed when the federal money runs out in 2024. Economists are predicting that this generation, with such a significant educational gap, will experience diminished lifetime earnings and become a significant drag on the economy. But education administrators and elected officials who should be mobilizing the country against this threat are not.

It will take a multidisciplinary approach, and at this point, all the solutions that will be needed long term can’t be known; the work of getting kids back on solid ground is just beginning. But that doesn’t mean there shouldn’t be immediate action.

As a first step, elected officials at every level — federal, state and local — will need to devote substantial resources to replace the federal aid that is set to expire and must begin making up lost ground. This is a bipartisan issue, and parents, teachers and leaders in education have a role to play as well, in making sure that addressing learning loss and other persistent challenges facing children receives urgent attention.

The challenges have been compounded by an epidemic of absenteeism, as students who grew accustomed to missing school during the pandemic continue to do so after the resumption of in-person classes. Millions of young people have joined the ranks of the chronically absent — those who miss 10 percent or more of the days in the school year — and for whom absenteeism will translate into gaps in learning.

In the early grades, these missing children are at greater risk of never mastering the comprehension skills that make education possible. The more absences these students accumulate, the more they miss out on the process of socialization through which young people learn to live and work with others. The more they lag academically, the more likely they are to drop out.

This fall, The Associated Press illustrated how school attendance has cratered across the United States, using data compiled in partnership with the Stanford University education professor Thomas Dee. More than a quarter of students were chronically absent in the 2021-22 school year, up from 15 percent before the pandemic. That means an additional 6.5 million students joined the ranks of the chronically absent.

The problem is pronounced in poorer districts like Oakland, Calif., where the chronic absenteeism rate exceeded 61 percent. But as the policy analyst Tim Daly wrote recently, absenteeism is rampant in wealthy schools, too. Consider New Trier Township High School in Illinois, a revered and highly competitive school that serves some of the country’s most affluent communities. Last spring, The Chicago Tribune reported that New Trier’s rate of chronic absenteeism got worse by class, reaching nearly 38 percent among its seniors.

The Times reported on Friday that preliminary data for 2022-23 showed a slight improvement in attendance. However, in some states, like California and New Mexico, “the rate of chronic absenteeism was still double what it was before the pandemic.” The solutions are not simple. There is extensive evidence that punitive measures don’t work, so educators may need a combination of incentives and measures to address the economic and family issues that can keep children away from school.

Researchers have long known that American students grow more alienated from school the longer they attend — and that they often fall off the school engagement cliff, at which point they no longer care. This sense of disconnection stems from a feeling among high school students in particular that no one at school cares about them and that the courses they study bear no relationship to the challenges they face in the real world.

These young people are also vulnerable to mental health difficulties that worsened during the pandemic. Based on survey data collected in 2021, the Centers for Disease Control and Prevention reported this year that more than 40 percent of high school students had persistent feelings of sadness and hopelessness; 22 percent had seriously considered suicide; 10 percent reported that they had attempted suicide.

Since the beginning of the pandemic, many parents and educators have been raising the alarm about the effects of grief, isolation and other disruptions on the mental health of their children. In addition to reconnecting these young people to school, states and localities need to create a more supportive school environment and provide the counseling services these students need to succeed.

The State of Virginia took a big swing at the problem of learning loss when it announced what is being described as a statewide tutoring program. But high-impact tutoring is labor intensive and depends on high-quality instruction. It is most likely to succeed when sessions are held at least three times a week — during school hours — with well-trained, well-managed tutors working with four or fewer students at a time. Such an effort would require a massive recruitment effort, at a time when many schools are still struggling to find enough teachers.

While tutoring is a step in the right direction, other measures to increase the time that students spend in school — such as after-school programs and summer school — will be required to help the students who have fallen furthest behind. In some communities, children have fallen behind by more than a year and a half in math. “It is magical thinking to expect they will make this happen without a major increase in instructional time,” as the researchers Tom Kane and Sean Reardon recently argued.

A study of data from 16 states by the Center for Research on Education Outcomes at Stanford University shows that the most effective way to reverse learning loss is to increase the pace at which students learn. One way is by exposing them to teachers who have had an extraordinary impact on their students. The center proposes offering these excellent teachers extra compensation in exchange for taking extra students into their classes. Highly trained, dedicated teachers have long been known to be the most reliable path to better educational outcomes, but finding them at any scale has always been difficult. If creative solutions can be found, it will help reverse learning gaps from the pandemic and improve American education overall.

The learning loss crisis is more consequential than many elected officials have yet acknowledged. A collective sense of urgency by all Americans will be required to avert its most devastating effects on the nation’s children.