4 Principals in 4 Years

A few weeks ago, our principal informed us that he would be leaving our school to become the Middle School Head at an American School in Shanghai. A search committee has been formed to find our next fearless leader. This next principal will be the fourth in four years at my school (the fifth if you count the principal who hired me, but who retired before my first day of school). What does such high turnover say about the being principal at my school?