How would that work? I can’t see how the surveillance software would distinguish a benign message from a malign one. For example ”you’re so cool” could be either a compliment or an insult, depending on the context.

Chat apps encrypt the messages as they are sent over the network preventing you from monitoring them.

This is where correlation would have to occur.

You see your son/daughter upset at 5:30 PM.

Suppose logs show your son/daughter was accessing IPs associated with Facebook/Messenger at 5:28 PM.

One could reasonably infer that something/someone upset them.