I'm a pointe fitter and I would turn away any student at 9years old.
Long term damage to their developing feet is a risk. Their bones aren't fused together and they can really damage their joints and bones.
Youngest I have fitted is 11 years old. She was a RBS associate so had been practising metatarsal exercises for two years previous. I fitted her with a soft shank beginner shoe. It pains me seeing young girls on social media doing pointe work. I had a mother trying to get me to fit her 8 year old. Absolutely not and I imagine she was doing the rounds with the dance shops, who all prob refused her.
Waiting and strengthening the feet has so many benefits. I know it's tough as they want to do everything NOW and feel like a real ballerina, but trust me when I say its more important to have strong intrinsic muscles in the arches and strong metatarsals.
Another interesting point I was taught was waiting until the girl has started her period as it shows a maturity of the body. Interesting as some girls can start very early and as young as 9/10yrs old.
Anyway good luck mums x