(CNN) There's more concrete evidence that the Covid-19 pandemic set American kids back.
Nationwide testing of a representative sample of fourth and eighth graders showed almost across-the-board declines in reading and math.
CNN's Ray Sanchez wrote an in-depth report on the latest results from the National Assessment of Educational Progress, known as "The Nation's Report Card," which follows similarly alarming results for 9-year-olds released in September.
The tests of students' math and reading were conducted by the National Center for Education Statistics between January and March, the first such assessment in three years, and they showed the largest decline in math scores since the tests were first administered in 1990. No state or large urban district showed improvements in math.
Racial and socioeconomic divides in US education are growing, which suggests the pandemic made the country more unequal. From Sanchez's report:
"What we're seeing is (lower performing) students ... dropping even faster and we're also seeing students who were not showing declines -- students at the top, meaning students at the higher performing levels -- they were holding steady before the pandemic or even improving," (NCES Commissioner Peggy) Carr said. "Now all the students, regardless of their ability, are dropping. That is the point we need to be taking away from this report."
There was one thing I was surprised the Nation's Report Card did not show.
"There's nothing in this data that tells us that there is a measurable difference in the performance between states and districts based solely on how long schools were closed," Carr said, per Sanchez's report.
People who cover this stuff -- here I'm referring to the nonprofit education news organization Chalkbeat -- pointed out NCES did not release data to double check that statement.
Anecdotally, it's true that drops in states where students went back to in-person classes earlier, like Florida, were not substantially less than states like California, where more students were out longer.
Chalkbeat did its own analysis of the report card data and argued there was some small correlation between school closures and test scores in fourth grade math and, to a lesser degree, in eighth grade math and fourth grade reading. It found no correlation for eighth grade reading.
That confounds what many parents might have expected and also previous reports on the deleterious effects of remote schooling. It also complicates the ongoing political argument over schools, funding and safety.
It should be a wake-up call that pandemic did not cause the problems in the US education system, but rather exacerbated them, according to Secretary of Education Miguel Cardona, who appeared on CNN's "New Day" on Monday.
School districts got big injections of federal money as part of the American Rescue Plan Act, and Cardona said they should use that money to address this specific problem. Plus, the government should continue to spend more on education.
"I'm calling on all leaders throughout the country to look at this as a call to action, to invest in education so that we don't go backwards," Cardona said.
Former Education Secretary Arne Duncan told CNN's Bianna Golodryga there should be a massive mobilization to catch kids up.
"We need a yearlong sprint between this fall and next fall, coming back to school on an individual basis, child by child, to do everything we can to help them catch up," Duncan said.
CNN's Brianna Keilar pushed Cardona about what the government can do to address a growing shortage of qualified teachers, particularly in rural districts and those with lower-income students.
"The symptom of teacher shortage is a symptom of a lack of respect for the profession," he said.
CNN has previously reported on the lack of qualified teachers in certain districts. CNN's Gabe Cohen talked to Stacy Brady, a biology teacher at Casa Grande Union High School in Arizona, where classes can have more than 70 students or may be taught by paraprofessionals rather than certified teachers.
Brady said if she was in a class without a teacher, she'd be hard pressed to learn without someone who could explain the subject to her.
"If there's nobody who has the content knowledge to do that, I'm gonna shut down," Brady said. "And I'm thinking many of our students might be shutting down as well."
In his TV segment, Cohen also featured an eighth grade teacher and mother from Long Island, Michelle Burke, who said there is a lot of pressure on children, which comes out in class.
"A lot of the things that we are seeing emotionally, behaviorally, are putting a huge strain on what you're seeing in the classroom," Burke said in Cohen's report.
While the problems are larger than the pandemic and predate school closures, this report card is part of the price Americans paid for the virus, according to Dr. Paul Offit, professor of pediatrics and the director of the Vaccine Education Center at Children's Hospital of Philadelphia.
Offit appeared on CNN to talk about the rise in cases of the respiratory ailment RSV that is crowding children's hospitals, but he also weighed in on the report card and pointed out that while children can get very sick from Covid-19, they are far less likely to suffer hospitalization or death than older people.
"I'd like to think we can be smarter about how to move forward with this so the cure isn't worth the disease," he said of the possibility of a future pandemic. "Because we paid an enormous price, and nobody paid a bigger price I think than kids."