Claire Reagan was feeling overwhelmed as her oldest child’s first day of kindergarten approached and with a baby on the way. The 5-year-old boy has autism, and she worried he would struggle with juggling in-person and virtual learning, and that she wouldn’t have enough time to give him the help he needs.

So she decided to wait a year before sending him to school.

“I was stressed about everything and then thought ‘Why does he need to start kindergarten?’ And it was like a weight was lifted,” said Reagan, a 36-year-old high school teacher in the Kansas City suburb of Olathe, Kansas.

Thousands of parents around the U.S. have made similar decisions, having their children delay or skip kindergarten because of the coronavirus pandemic. The opt outs, combined with huge declines in preschool enrollment, are raising worries about the long-term effects of so much lost early education.

“If there is a group for which you would be particularly concerned, it is these very young students who are not having these foundational experiences,” said Nate Schwartz, a professor at the Annenberg Institute for School Reform at Brown University.

Kindergarten isn’t required in most states, and in normal times parents sometimes “red-shirt” children who would be young for their kindergarten class to give them an extra year of developmental readiness. But enrollment numbers have plunged in many places this fall as parents weigh health concerns and the prospect of helping young children to navigate distance learning while also holding onto their jobs.

In Los Angeles’ public schools, kindergarten enrollment is down about 6,000 students, or 14%. In Nashville, Tennessee, public kindergarten enrollment is down about 1,800 students, or 37%, from last year.

According to a University of Oregon survey conducted in early September with 1,000 parents from around the U.S., including 242 with a child who was supposed to start kindergarten this fall, 17% of respondents said they were delaying their children’s schooling. Among those, the most frequent reason cited was safety concerns, followed by concerns about managing virtual schooling and other responsibilities, according to Philip Fisher, a psychology professor at the university who is leading an effort to measure the effect of the pandemic on young children and their families.

Fisher said the vast majority of parents reported that they were making sure their kids were attending all of their virtual lessons and completing their coursework without the assistance of hired help or other adults, making juggling their own work a challenge. He said that parents are overwhelmed, particularly those in low-income communities where schools are more likely to be offering only remote instruction.

“We think young kids are likely getting lost in the shuffle,” he said.

Reagan, who is also keeping her 3-year-old daughter home from preschool, said she held off with kindergarten for many reasons, including her own pregnancy and instructions to quarantine for two weeks before she delivers in the fall. She said her job allows her to work from home and her family has insurance that will continue to pay for some of her son’s therapy.

For many young students, the delayed start of primary school follows a disrupted preschool experience. Among preschool-age children, participation rates plummeted in the spring, as programs closed and children stopped attending, according to a report from the National Institute for Early Education Research at Rutgers University. The group is planning a follow-up report, but all indications are that enrollment hasn’t fully rebounded, said Steven Barnett, senior co-director of the institute.

He said public preschool programs such as Head Start have been “substantial equalizers” for low-income families.

“When that falls apart, parents are not going to be able to fill the gap,” he said. “The people who are dependent on free public education as equalizers can’t make up the difference when left on their own.”

Some parents feel their children may be ready for in-person school but not for virtual school, said Anna Markowitz, an assistant professor of education at the University of California, Los Angeles.

“They are thinking I can’t work and monitor my child’s Zoom schooling. Parents are really in an impossible situation,” she said.

Only 17 states and Washington, D.C., require children to attend kindergarten, Markowitz said. Parents elsewhere can bypass kindergarten and just send their children to first grade next fall. In a typical year, only about 4% of children who are eligible to begin kindergarten are held back by their families, said Chloe Gibbs, a Notre Dame economist.

The National Academies of Science, Engineering, and Medicine released a report in July focused on younger children. Its advice was to prioritize the reopening of schools for children in kindergarten through fifth grade with well-funded safety measures in place. But since the report was released, high rates of community spread have made in-person learning more risky in many communities, turning young learners into virtual learning guinea pigs.

“When you look at the distance learning research, very little has been carried out on young students, even below middle school,” said Brown University’s Schwartz, who is a member of the committee that wrote the report and is also running a project that provides research to school leaders who are trying to make decisions during the pandemic. “Few people were even considering that it could be considered with kids this young.”