I don't see the solution here. You physically watch your children 24/7?
I dunno.
Especially with smart-phones.
I remember Mark Fruenfelder from Boing Boing was talking about this, he's got kids, and is Adam Ant - kids can only use internet in communal areas of the house.
I think this is a good rule.
Ultimately, kids are going to check out pornhub or something similar, the same way as we managed to get some shitty VHS tape from a friend of a friend. But hoping that an ineffectual filter is going to solve the problem is just a way for piss poor parents to bury their head in the sand and for "well we must do something... and this is something" government types to pat themselves on the back.
I think this breaks more than it fixes