I put my student on between the ages of 13-15. Depends on their strength, technique and experience. What age did you go on Pointe? If you are a teacher, when do you advance your students?
I went on pointe when I was 10. I had been taking regular classes for three years. Pointe was a half hour class once a week. It was very slow and careful. Our teacher made sure we sewed our own shoes. I've taught students pointe at age 10 and up (ten in a professional full time school) and I've taught adults in their 50's. VERY slow and careful. I really could appreciate how much they wanted to get into pointe shoes. They never got away from the barre, and they loved every minute of it.
Also I want to add that with adults, it was a very small class and easy to watch everyone, and with the ten year olds I had assistants. Otherwise it would not have been possible to do this.