The narrative says that phone use was already banned during classroom instruction in many of the schools that later instituted school-wide bans. The impact on students would've been minimal because realistically the only time they would've been able to use phones beforehand was passing between classes or at lunch/recess.

Though this is still relevant to policy-makers who are thinking of instituting district-wide bans. It's sorta like all the heat around critical race theory: banning something that doesn't actually happen much in schools.