Visit a foot health professional. An podiatrist or foot orthopedist can evaluate your arches and tell you about conditions or ailments that might be holding them back from full extension.
Work on your arches with an expert. Colloborating with a physical therapist or osteopath can help improve your ankle extension, which will improve your ballet arch.
Strengthen your toes. Ask your ballet instructor for ways to work on your toe muscles involved in the tendu and pointe postures, such as point flexes and releves. Exercises with Therabands also improve toe power. Over time, such exercises can make your ballet arch more appealing.
Wear your pointe shoes as often as possible. By breaking in and eventually wearing out your ballet shoes, you force your feet to exert more effort to maintain the "en pointe" posture. Doing so works your arches and improves their shape.
Stretch your feet in ballet slippers after your work on barre. Stand parallel to the barre, and slowly bend into a demiplié. Holding the position, raise your feet off the floor as high as you can. Maintain weight on your two biggest toes. Avoid wobbling. Straighten your knees while maintaining your foot's shape. Slowly reverse these movements, then repeat eight times.