Prevent kids from turning VPN off

All of the child prevention apps monitor traffic through VPN, and all kids have to do is turn off the VPN and they are free to do what they want on their phone. I couldn't find out how to prevent my kids from turning off the VPN required by the Bark app. However, I think I figured it out. Perhaps someone can help me and reply if this works for you or if there is another way to do it.

I've setup the parental control to prevent the editing of the VPN characteristics but I can't prevent them from turning off the VPN which render the whole idea of parental control mute.

Please tell me that iOS has something I can do.