[graybeardhacker]

If I understand the graph correctly, it looks like there's maybe a three percentage point increase. But given there is a 1 percentage point delta in the pre-ban data, that would seem to indicate there is at least a 1 point variation that must be ignored as irrelevant.

I'm not sure how they generated the error bars but that, to me, would suggest the relevant error could be +/- 1 percentage point. Meaning the delta could be at little as two percentage points.

My intuition says cellphone bans would have a positive impact, but I don't think I'd call this data conclusive. I'd want to see more data from earlier and later.

Also, if these are the same students, then test scores might be reflecting increased maturity. If it's different students of the same age, it could be a shift in some extra-educational factors affecting the younger generation.

Too many unknowns and not enough signal.