My son has always done a fantastic job, confirmed every 6 months by the dentist, so I was satisfied that he was doing them properly. Same with washing, I didn't just say hey you're 9 years old, time to do all this alone. Once I was satisfied he was capable of doing it properly then I let him do it alone. I've never heard those recommendations though, maybe that's something that should be more readily promoted, like the dentist should tell you at each visit or something, or the posters should be on the wall in the waiting room. The only thing that's ever been mentioned was the health visitor asking when he was 2 how he was brushing teeth and I said he was quite keen on it and they after i had brushed them he liked to have a go himself and she said "you'll be doing them for him for a few more years yet"