Depends a bit where you live I think. Here in Switzerland smartphone ownership among kids is less prevalent than say in the US. There's mostly consensus that we're not doing the kids any favors. But the peer pressure is just there. Also it doesn't help that some schools use WhatsApp for in-class communication.

Depends on where you live.

My nephew didn't have an smartphone until he was 12-13 I think.

He had a tablet at home and a switch though.

There is a region-wide push to prohibit smartphone usage for primary school children (<12yr)