You speak for your own place but you know as well as I do there are a great many places where the pressure is coming from the parents. I had two sets of parents take their children out because we wouldn't put them in for a grading we know they wouldn't pass, not even marginally as they had taken weeks off. One mother was furious with me and got abusive, (she shouldn't have done that really I threw her off the camp lol. . . Crown property) her little darling had the right she said to get her next belt, I actually said she could have whatever belt she liked out of our stock even black because the only person she was hurting was her daughter.
I'd argue that children are only better at one aspect of martial arts than adults as they are more flexible and athlethic which is fine if your martial art is a 'sport' one but I really don't think children are mature enough to be black belts under at least 17. Children however many dan grades they have can't teach an adults class, can you imagine a 6 year old 3rd Dan teaching my MMA students? and before you say that MMA is different we do karate, TKD,Judo and BJJ etc etc in that and the Dan grade should be able to teach what they are graded in.
The deeper understanding isn't there that requires maturity, something no kid of 5 or 6 is going to have, it's a farce having Dan grades of that age.
Do the youngest have the ability to work out the Bunkai of their patterns/katas? Do they know the Bunkai of their patterns/katas even? Do they truly have the gravitas to teach at five years old with a black belt tied round their waist, what would they teach? gymnastic movements or true SD and fighting? Can they teach for two hours on end, running through a syllabus acording to the grades in the class? If you have never done that I wouldn't be quick to say a child could.
You will never convince me a child can be a proper black belt nor that a child should even get a black belt let alone multiple Dan grades.