Paper: https://www.nber.org/papers/w34388

Back in my day (when we walked to school uphill both ways), we weren't allowed to carry around basic flip phones. They had to be in our locker and only used before or after school.

When and why did it become acceptable for much more distracting and stimulating devices to be allowed in class?

My interpretation is, the pandemic is a root cause of lower test scores for many reasons, one reason is that kids started using cell phones way more during the pandemic, and that new stuff on the phone (TikTok, let’s be real) causes lower test scores. Reducing usage during school is addressing a real problem, but it’s one of many real problems, and some are way bigger.