The point of banning phones in schools was eliminating the distraction and increasing student engagement, not fixing their mental health.

Theyre still addicted to the square the minute they get out of school, obviously. So thats bad for their mental health. Schoolkids before smartphones also didnt exactly have the best mental health anyways, so Im not sure why its considered an important metric.

What matters is whether or not banning the phones increased the amount kids are actually learning and focusing on education and socialization. Their mental health is largely irrelevant in that discussion

Because students are mostly listening to the teacher, not using smartphones in the school anyway.
Some people just love bans.