What is an efficient school?

Here is a link to an interesting Ed Week article about measuring the efficiency of schools.  So, what does it take to provide a quality education for all at the least cost.  Certainly, schools can complain about not having enough money, but what does tell us when a school is using money wisely and most efficiently.  What are best practices in using money well and providing good outcomes for students?  Read the article and see what you think.