Kids can’t get past a filter without full computer access
That is true in most cases, but I know of cases where kids bypasses the admin by rebooting the entire computer manually. But if the child figures out the parent’s passwords, they can do what they want. So inasmuch as if there is one computer in the house, with access limited in terms of time and content, technologically minded parents, and constant vigilance, then I admit the risks are diminished, if not eliminated.
But children are not stupid. I certainly could have got hold of my parent’s passwords, one way or another, had I put my mind to it. And if there are multiple devices in the home, if there is any lapse in concentration, if the child spends too much time on it, if the filter is anything less than completely foolproof (and most aren’t), then the risk becomes enormous. And how many homes can honestly claim to have taken every possible precaution? In my experience, they represent a tiny minority.
And so my point remains. The pros of the internet (as far as domestic use is concerned) are anyway minimal and arguable. The risks, even in a very careful home, are huge. So, to go back to the original point, just don’t do it.