VPN is an acronym that is being used more and more in conversations about technology. Although commonly used to access work networks over the internet for years now, they are being used in many situations by younger people, and it could be worth a little read on what they are and how they are used.
VPN stands for Virtual Private Network and they can be used to hide net traffic and what sites and services are accessed, even if parental controls have been put in place.
There is only a very tiny chance that any primary-aged children are using such a service (mostly due to the cost and payment requirements – however, there are free ones out there), but I know that such things are discussed and used in teenage years by individuals, sometimes for reasons that are concerning.
The latest article from ParentInfo gives a very brief introduction to VPNs and worth a read to get up to date.