Nobody really knows how exactly many teachers drop out of the profession. A couple of recent articles are keeping this issue in the spotlight, which is a good thing:
This from the conversation
And this a reference to the Gallant and Riley study (Monash).
50% in the first five years is a figure thrown around, 30% in the first three years is another. And unfortunately there is reason to believe that many of the leavers are good quality teachers.
How to keep them in the profession?
Some suggestions that have been raised: increase salaries of experienced teachers and finding a way for society to recognise the professionalism and technical skills required for the profession, giving them the social status they ought to have.
Many ideas about what it means to be a quality teacher are very well articulated in this article by Raewyn Connell.