> http header indicating that the client is a child-locked device

what happens when the request goes through a proxy and that proxy is configured to strip this header?

Websites that don't cooperate would need to be blocked by child-locked devices. That part wouldn't be any different from today.

Do you even know what a proxy is? It has nothing to do with website cooperating or not

The Web is HTTPS now, so that can only happen if either the origin server or the user trusts the proxy.

User uses a proxy to bypass the client side validation, that’s the first thing I would have done as a teenager