It is easy to implement, easy to monitor, and will probably just work if the government do the effort to monitor and enforce it. If not, it will just be an other DNT header
Sorry, no.
As always with security, perfect is the enemy of good. A good set of hard to change - for children - client-side filters would do wonders in terms of real improvement. As much as I'm tired of the LLM hype, they might actually be a good fit for such tasks.
It's the parent's computer and they have a right to put a password on the BIOS and a child lock on the system that forces these types of headers, with no available bypass for the child account. Or, if they do please, have the router filter any website outside of a whitelist without a password.
We do worse for OpSec all the time?