I'm not sure what you're on your soapbox about, but this decline is probably due to the enormous disruption in children's education caused by the Covid pandemic. The report even compares pre- and post-Covid achievement rates.
> this decline is probably due to the enormous disruption in children's education caused by Covid lockdowns.
FTFY
A distinction without a difference. Many parents were keeping children out of school regardless of lockdowns, so it wasn't only lockdowns that contributed.