Preliminary research suggests students nationwide will return to school in the fall with roughly 70% of learning gains in reading relative to a typical school year, and less than 50% in math, according to projections by NWEA, an Oregon-based nonprofit education-services firm. It expects a greater learning loss for minority and low-income children, who have less access to technology and whose families are more likely to be affected by the economic downturn.

About 26 million public-school students, just over half in the U.S., are considered low-income and rely on free or reduced-price meals at school.

Dr. Greene said there could be a mix of in-person and remote learning in the fall, and his goal is to make sure all students can get online and have devices to learn on. But he worries that providing laptops to students could make them vulnerable to crime.

“That puts a target on them,” he said. “I’m stunned at the number of devices and the amount of equipment we’ve lost just through burglaries” at school.