Number one, is safety.
Is the student ready to safely work at this level?
“The bones of the foot are not fully developed, strengthened and hardened until sometime in the teenage years. Naturally there is a great deal of individual variation. If a young dancer attempts pointe work without proper strength and technique, there is a chance that she will permanently damage those not fully developed bones. Body weight times momentum creates a great deal of force.” - When To Start Pointework? Gaynor Minden FAQ
“Students attempting pointe work before being ready risk, at the very least, building bad habits which may take years to correct. More serious is the potential for injury or permanent damage to the bone or muscle structure of the foot, which far outweighs the risk of disappointment.” - To The Pointe by Janet Parke
Though teachers may have their own set of criteria, these requirements are widely accepted within the dance community:
At least 11 years of age.
At least 2 years of serious ballet training.
Taking at least 3 full hours of ballet per week.
Responsible enough to bring all ballet equipment needed.
Dresses appropriately for class.
Attentive in class and applies corrections well.
Read full article here: http://www.danceadvantage.net/pointe-readiness/