I’m no libertarian, but I can’t think of any way short of shutting down the Internet that would be an effective way to prevent porno access from those of any age who seek it.
For my own children, they must get permission for each and every web site they go to. No private email. CERTAINLY no social media.
You are a great parent who cares
It’s sure a far cry from my youth, where if you wanted to access porn you had to bribe somebody’s drunken uncle to travel downtown to the red light district and bring you back a couple of magazines an a brown paper bag.
He who controls the router controls what comes into the house.
I don’t see why all porn site addresses don’t start with “xxx” instead of “www” or at least have the start www.xxx...then whatever. Then they would be easy to filter. I wouldn’t restrict their content at all. However, if you want to access it you must type the xxx. I’m no expert, but this seems easy.