higher Elementary grades in 2020 the most (those applying to college in 2024 and later) as the attached analysis shows.
Don't forget that vaccines didn't arrive until Dec. 2020 and not widely until the middle of 2021, thus leaving ALL teachers, parents and grandparents vulnerable to super-spreaders like schoolchildren...and anyone with kids knows this reality. btw, thanks for volunteering in one of those trials...it helped a lot of people.
Link: https://www.brookings.edu/articles/learning-curves-post-covid-learning-trajectories-differ-by-the-grade-a-student-was-in-when-the-pandemic-hit/