In home dog training

I was doing an in home session for a family with a dog who growls at the kids each time the kids pet him, or play with him or hold him...

I was talking to the family (kids approx 6 and 8 included) and I was talking about reading a dog. The obvious things we see and hear are things that may come just before a final warning or in some cases a bite.... etc etc (without going into too much detail on this part).

I was talking about the physiological change with the the dog, prior to any physical warning we may see... blah blah blah.... kids says, "oh its kind of like two people a Spanish person and an English person, neither of them speak the same language, you have to communicate using expressions and body language..."

Now what is it that an adult does not get in all this? That's all it took and two hours later the child was communicating with the dog understanding what the dogs was comfortable with and what the dog had enough with!