Although some give an age that is typical for being ready to go en pointe (opinions range from 10-13), it is something that is very different depending on the dancer. The proper strength and placement is necessary for safely dancing in pointe shoes, so some dancers may be ready later than others of the same age group.
Many schools allow students to begin wearing pointe shoes before they are physically ready. This can be detrimental to the dancer later on, especially since most students are still growing when they begin pointe. If a student starts pointe before they are strong enough, they can easily develop poor habits and even serious injuries.
A dancer ready for pointe should be able to stand in releve in turned out second position and create a straight line from their knees to the balls of their feet, with the arch of their foot not falling below that line. The dancer should be able to easily perform multiple releves on one foot onto a high demi pointe without losing strength in their core, turnout, or compensating placement in their spine and hips.
There are many other signs that teachers look for to determine if a student is ready to start pointe, so it is important to consult with a trusted teacher first. Although it may be hard to hear that your student may not be quite ready, it is always a decision made in the dancer's best interest.