One thing I don't understand: if you and other parents are so concerned about this... why let your children use those sites?

This feels equivalent to “if you don’t like smoking, just don’t smoke”.

Like I said in my original post I don’t think this stuff is specific to kids. I think social media has an equivalent to “second hand smoke” that poisons society whether or not we individually engage with it. And yes, classrooms are full of it.

I'm assuming you don't have kids? It's impossible to stop them, both on a technical and social level. You'd guarantee a destroyed relationship with your kids if trying to do so without their consent.

This describes the exact purpose of the law: to stop letting kids use those sites.

My very strict uncle was adamant that my cousins stay off Facebook when they were kids. They got on anyway. When he eventually found out, it was a bad situation. If he couldn't stop his kids from getting on, only the websites themselves can.

Peer pressure will cause many children banned from using social media to work around the ban.