In September 2022, the U.S. Department of Education has released data indicating that average reading scores for 9-year-olds slid to 215 out of a possible 500, and to 234 in math. These are the sharpest declines noticed since 1990 and are largely attributed to the disruptions caused by Covid pandemic. A study by the Annie E. Casey Foundation in 2011 revealed that 16 percent of students who lack in reading proficiency in third grade fail to graduate from high school on time ­– four times higher than proficient readers. OECD in its September 2020 report has provided direct evidence on the effects of closed schools and the potential economic impact. In the American Rescue Plan, the U.S. has earmarked $122 billion in federal grant for K-12 public schools and mandates that at least 20 percent should be allocated to addressing learning the loss of learning. Many states are also launching their own programs to alleviate the problem, for example, offering up to $1000 to enroll in private tutoring, beginning the day by working on multiplication tables etc. 

Additional reference: https://www.wsj.com/articles/schools-are-back-and-confronting-devastating-learning-losses-11662472087