As someone trying to start a porn-free-coaching business, I know my way around this topic.
Firstly, the age for first contact with porn is down to 9/10 in many western countries. With kids having smart phones one unsupervised kid is enough to bring smut into the whole school.
Secondly, it’s next to impossible to safeguard your children if they have access to modern technology, even if just through schoolmates. Elsagate (Google it) is just one case that shows how predators bring cruel or pornographic content in the life of children looking for innocent videos.
Thirdly, most apps designed to stop porn can be circumvented. Especially since kids are more natural to tech and find solutions more easily (if the parents aren’t into that stuff as well).
When I started to break my porn addiction, I couldn’t find one app, that wasn’t circumventable.
When we found one, described as uncorruptable, my fiance found a way to do it in a couple of days.
My conviction is, that the only save way is open communication. Giving your children a healthy view on sexuality, explaining the dangers of porn and that it destroys the beauty of intimacy when they are old enough.