(CNN) The first-grader was finally getting to grips with reading. He'd made "enormous progress," said his special education teacher Jill Marangoni, who'd spent months working with him in New York. But then coronavirus closed the schools.
Seven weeks later, "he's forgotten a lot of his sight words," Marangoni told CNN. "He is already back to those very basic reading skills where he's having to sound out every word. It's disappointing to see because he will be moving onto second grade next year and he's now going to be nearly two years behind."
Marangoni usually has a caseload of 25 students, but with some of them unreachable at home she's down to working with just 10 children now. And she's seeing some others fall behind.
The big fear is that the annual "summer slide" could supercharge the loss of learning for students having a hard time keeping up with their education in the lockdowns.
In interviews with CNN, experts said academic losses could be particularly problematic for grade school students who should be in the process of laying critical foundations of reading, writing, and math skills that should be built on for years to come -- potentially robbing a generation of students of vital stages of learning.
"It's kind of a double whammy of starting to forget and losing that kind of academic mindset of being out of school, and missing out on a couple of important months of instruction," said Megan Kuhfeld, a research scientist at the Northwest Evaluation Association's Collaborative for Student Growth Research Center.
"Come fall ... teachers may have students in their classrooms who are grade levels apart in their learning."
Using existing data on learning loss typically seen in the summer from a national sample of over five million students in grades three through eight, Kuhfeld and her colleague, Beth Tarasawa, predict that extended school closures could potentially cause serious academic setbacks for students struggling to adapt to remote instruction. In a worst case scenario, they may retain only 70% of the gains they had made in reading and only 50% of the gains made in math.
Math could be a particular sticking point, Kuhfeld said.
"It appears that math is something that parents don't feel as comfortable doing with their kids," she said. "We find that math is often something that parents view as the school's domain to instruct students on. So typically, when school is out, math just happens less in the home than reading."
Teachers and parents told CNN that their children are struggling to learn at home -- especially those with special needs or those who are used to interventions that depend on hands-on instruction.
"Their written language is really taking a hit right now," said Marangoni, whose case load includes students in first through fifth grade. "Fifth graders that were strong writers in school, who would never have turned in anything without editing it first -- you see what the work they're turning in. It's missing capitals, it's missing punctuation, run on sentences -- just lacking that quality that they had at school and that they just don't have now."
Beth Scott, a mother of two, said she worries about her 8th grade daughter, who has dyslexia, keeping up with her peers.
"It's hard for her to focus on her own without having someone there to kind of guide her," Scott said. "Even though she has made great strides through the last five or six years ... she will be behind again. I feel like it kind of takes us back a little bit to several years ago, when we had just this year entered all mainstream classes and now she's trying to keep up."
And it's not only parents and teachers who are worried -- children know that virtual learning isn't necessarily cutting it.
"I had a second grader say to me, 'Miss M, do you think I'm going to be allowed to go to third grade?'" Marangoni recalled. "'Um, am I doing OK? Am I going to be allowed to go to third grade?'"
Educators said that students with resources are struggling to focus at home, but lower income kids are suffering the most right now.
"The inequities that we already were dealing with -- that we already knew about -- Covid is compounding all of these inequities," said Sarah Crichton, who teaches US history to 11th graders.
She said her students in Brooklyn, New York, have had parents sick with coronavirus and have had to take care of younger siblings, or initially didn't have access to a computer or continue to deal with spotty Wi-Fi -- all making effective distance learning impossible. "We're not trying to add additional stress to their lives right now."
In other words, the "covid slide" has the potential to widen the inequality gap in achievement if meaningful steps to disrupt the status quo aren't taken, experts caution.
Kufeld and Tarasawa at NWEA said they hope their research on potential learning losses will offer insights to think through ways to mitigate the effects of extended school closures right now.
In their paper released in April, they recommend that "policymakers, educators, families, and communities should further their work to provide support, especially in mathematics, to students while school is disrupted."
NWEA has also gathered a number of tools and resources for parents to use at home -- everything from free reading courses to free access to math textbooks.
Teachers said while they are concerned about their students during this challenging time, they are prepared to rise to the challenge come fall.
"It's always been the case that when we start school in September, we have students that have lacked some prerequisite skill," said Crichton, "but the teachers in my school -- I think already have a lot of experience in trying to bridge those gaps the best we can."