Thank you, Cynthia.
It is disappointing when we work with a student for quite a while, see some real progress, and than find that the student simply disappeared. We cannot get through to every student, nor will we always know why a student opts out of the program. If you are confident that you did all you could to help a student, (and in this case it seems like you did), you should not feel you let the student down.
Your positive influence may yield the results you hoped for at a later date. The student knows what you did for him.
