https://www.brookings.edu/articles/the-pandemic-has-had-deva...
> Nine-year-olds lost the equivalent of two decades of progress in math and reading, according to an authoritative national test. Fourth and eighth graders also recorded sweeping declines, particularly in math, with eighth-grade scores falling in 49 of 50 states.
https://www.nytimes.com/2022/11/28/briefing/pandemic-learnin...
> By the spring of 2022, according to our calculations, the average student was half a year behind in math and a third of a year behind in reading.
https://www.nytimes.com/interactive/2023/05/11/opinion/pande...
> Students “lost out on about 35% of a normal school year’s worth of learning” when in-person learning stopped during the public health crisis, according to a paper published Monday in the journal Nature Human Behaviour.
https://www.cnn.com/2023/01/30/health/covid-learning-loss-st...