I blame technology.
Call me old fashioned but I don't believe information soaks in the same way when using electronics.
There are too many distractions. When reading material, it is easy to rely on control F at the detriment of understanding the subject as a whole. You type faster than you write so the information doesn't really sink on when making notes.
Could just be me but that is my experience with both methods. I feel that in trying to reinvent the wheel, they've moved away from the essentials.
The effects of covid must also be considered. Learning remotely is difficult. For children who are reliant on being in school to learn, that's going to hurt.
My last semester at UTSA prior to Graduation, due to Covid I was forced to take my Final 3 Courses online. It was brutal, had a hard time focusing and taking notes. Easily the most challenging experience I faced academically.
I can't imagine the difficulties of small children and teens being forced to sit in front of a computer screen for 8hrs/day, 5 days a week, for 9 months, and it not have a negative effect on their ability to retain knowledge, as well as being able to properly focus.
At the end of the day, Black Students have been gradually declining in Reading and Mathematics, this just exacerbated the issue. There was a thread recently about the high % of Black Students graduating High School. On the surface that is promising, but at the end of the day, many of those students are ill-prepared for the real world, barely reading at an 8th Grade Level.
The effects aren't hidden either. Youngins today have very poor social skills and communication skills. The way they speak, ending sentences with "duh duh duh duh duh", to make up for not knowing how to express certain thoughts, it is sad.