That's true! Not only the dad or mum who's supposedly teaching their son or daughter,but also some professional ones.
When i taight my eldest to drive I was a class 1 police driver. I had no teaching qualification, but as a driver I was more highly qualified than pretty much any DVSA licemced instructor. She was pretty sensible, we didn't bicker or argue, and she passed first go.
Your average high street driving instructor is usually no better qualified a driver than any reguar driver. Their qualification is a teaching one, not a driving one and they are no more skilled a driver than the norm. Those with advanced experience and training are fairly niche and deliver to a different market to those teaching new drivers the ropes.