Telephones did not record, but they did have a log of incoming and outgoing numbers. So it was possible to check if a child was suddenly talking to someone new.

> I guess the argument would be technology enables children to do secret stuff without any of the obvious signs, like sneaking out in the middle of the night?

Yes, it was rather obvious when a teen was behaving secretive, or there were middle of the night calls.

Privacy is important, but if your teen was suddenly displaying secretive behavior you could tell.