The mass experiment in remote learning was an unmitigated disaster, according to a new report by the consulting firm McKinsey & Company. The report quantified the harm done to children of all grade levels, and demonstrated negative effects to all facets of education.

The report examined test results in first through sixth grade across 40 states, comparing 1.6 million elementary students’ testing performance to pre-pandemic student scoring. The results showed that the children who learned remotely as a result of school lockdowns were about four months behind in reading and five months behind in math. The children in the study learned remotely in time periods ranging from months to a year.

The past year’s COVID lockdowns also disproportionately affected minority and low-income school districts. In math, students in majority black schools concluded the year six months behind, and students in low-income schools ended seven months behind.

Older students failed to attend class at more than double the rate from before the pandemic. The number of chronically absent 8-12th grade students increased from 3.1 percent to 5.4-7.7 percent.