I'd say RFK Jr was on the right track.
Yep, the masks sure did help to ruin the lives of American
Children. How many years are American children behind with the 3R's compared to the rest of the world? Last I heard it was at least two years.....

Disturbing study shows scores in three key cognitive tests slumped between 2018 and 2021, with face mask rules among possible culprits'

dailymail.co.uk: Face masks DO harm children's development: Study blames them for 'significantly reduced' development...

Several points here. Yes, masking at school was not ideal in terms of the degree of learning and social interactions that normally flourish in a school setting. But the lengthy total shutdown of in-school education and doing it all by zoom from home....for those families with computers....that preceded masking at school had a far more profound impact on progress than masking did.

And even the quote you give from the Daily Mail (which has a terrible terrible rating for.....poor reliability and substantial disinformation) says that the face mask rules were among POSSIBLE culprits.

As an aside....do you really think that the US was the only country that required masks in schools? Try adding Italy, France, Belgium, Spain, and Germany. And that's just Europe. We know that Asian countries also required this.
theguardian.com - Masks for school students mandatory in several EU countries

I call that an "aside" because the study that the Daily Mail describes did not compare the performance of American school kids with school kids in other countries. It was a ridiculously small number of kids providing pre-pandemic baseline scores (only 605) to 118 kids during the height of the pandemic (which was zoom time), and then 39 younger kids assessed through the end of 2021. And the "shocking results" that this tabloid refers to are tabloid-talk, and not the study conclusions.

Your confidence in this publication supports your prejudices, not the truth.