There may be strong psychological reasons to forbid children and teenagers from using smartphones.

The article says "children", but clearly intends teenagers as well; the French prohibition on using smartphones in school includes high school. If we want teenagers to become capable people, we should not infantilize them by calling them "children".

I think the same kind of argument applies to portable phones. They may not be designed to be so addictive, but we should not get our children in the habit of letting Big Brother track them. We hope they will grow up to be activists for good causes, which means they will have something to hide, though not a shameful something.