Famously children can only access internet from wifi paid for by their parents.

I'm not for these draconian age verification nonsense, but this isn't a valid argument.

This is the answer. If you provide internet access to someone, you're responsible for it. It's a generally established law from a Torrenting PoV, so isn't it equally applicable to downloading content unsuitable for children. Sure it'll destroy offering free wifi, but that always was tricky from a legal PoV around responsibilities.

Ideally the law would require websites (and apps) to provide some signed age requirement token to the client (plus possibly classification) instead of the reverse. Similarly OS and web clients should be required to provide locked down modes where the maxium age and/or classification could be selected. As a parent I would the be able to setup my child device however I wish without loss of privacy.

Is it bypassable by a sufficiently determined child? Yes, but so it is the current age verification nonsense.

> if you are paying for internet access you have to be over 18, no?

No, that's not the case.

unless your kid never goes to public school that isn't true