Some physicians and public health experts have said that the emotional and cognitive effects of keeping schools closed are far greater than the danger of transmission inside schools, which the CDC has previously found does not occur as long as face masks are worn and other common-sense measures taken. As schools have remained closed in parts of the country, those alarms have grown louder. “The consequences of social isolation and school disruption for kids have been devastating,” wrote the pediatrician Hansa Bhargava last month, as many public school districts approached a year of fully or partially remote instruction.

The new study suggests that isolation and inactivity are key culprits in that crisis. Published on Thursday by the CDC, the findings were based on a survey of parents whose children either attended in-person instruction, took all their classes via computer or were participants in a so-called hybrid model that combines both remote and in-person instruction. It found that for both virtual and hybrid models, children were more isolated, spending less time with other children and outside. They also simply moved less. (The new study included children between the ages of 5 and 12.)

“These differences in physical activity are concerning,” the researchers wrote. They also noted that students of color were more likely to be engaged in remote learning at about twice the rate of white students, meaning that they were more likely to suffer from the psychological effects of learning from home than were their white counterparts.