They also did read more to their kids in 2020 vs pre-covid. However, I can't find data suggesting that they continued reading at that rate through 2021 and 2022.

Another stat did suggest that low income kids had a harder time keeping up during covid. Factors included family members who did not know English, fewer books in the home, and low literacy rates among parents (making it hard for them to read to their kids), and more media consumption (a major factor in poor development among very young children).

So, if we put everything together, we could assume that kids in low and probably middle income families were at a disadvantage compared to kids in high income families. Since they make up the bulk of the student demographic, they were likely responsible for the drop.

If the situation at home remains bad, I'd expect these scores to continue to drop compared to previous years and other countries.

I'd say that for those families, the pandemic didn't help, but those problems were there well before covid.