What makes the best kids smartphone?

Your kid doesn't need a phone. If you want them to have a phone, then a flip phone that allows them to call you.

No smart phone. Get a flip phone if you need to be able to call them.

Dumb phone. Cheap, durable, and they work.

In all seriousness, there has been a correlation between the age that a child receives their first phone and depression.

Which was subsequently debunked like most other things related to this.
Everytime kids and tech comes up there always seems to be another wild theory about it.
- Yeah, also correlation is not causation. I know its an old trope to bring up but it is true. You can find a lot of correlations in science and research, they don't need to make sense.

I got my kids SyncUp Kids watches recently. They allow my kids to text or call me, my wife or each other. They also have a few very simple features on there to keep them mildly entertained without being too distracting. They also give me alerts when they leave and enter certain areas like home and school, and have an easily scheduleable school mode that turns off all distracting features when they are in school. All in all, they're pretty good.

People saying flip phones. But search for grey scale e-ink phones. Pretty sure they can only handle apps the company designed for them. Battery life is forever. And they can practice using their pocket computers.

Lots of people are opposed to smartphones but they are fine in my opinion as long as they get checked frequently and you don't allow social media until a certain age.

If the kids are smart and they want to, they will circumvent such „social media is not allowed“ rules easily.