'if my son has a VPN installed on his computer....'
i would get him to remove it. not just because he could access adult material but because free vpn's (paid need a debit/credit card) are notorious for scams/hacking purposes. there are 'good' ones typically web browsers such as opera has a free one. most free ones though are harvesting personal info to varying degrees.
I posted this the other day; it explains some of the ins and outs (as well as pros and cons) of VPN's.
-- The only winning move is not to play. No system is 100% secure Ridicule is nothing to be scared of - Adam Ant The only thing constant - is change. Chris Evans The internet is a series of tubes Windows Update isn't rocket science - if it were, it would work. Unlike Monty Python, spam is never off. Some video posts may contain swearing/inappropriate content for young children
If my son has a VPN installed on his computer, will the child safe on websafe security block adult websites?
Just because he has a VPN installed does not necessarily mean it is being used to access inappropriate content, for example it maybe used to access appropriate content that is geographically locked to specific location. If it is being inappropriately used then its removal alone will not solve the problem and other stringent controls would be require, for example limiting use of devices to commonly d frequent spaces at home.