CLEVELAND, Ohio -- How is value-added calculated? The goal is to find whether a student made a year's worth of academic growth in a school year, but there are many different methods you could use.

The concept sounds appealing: Measure the effectiveness of schools and teachers based on the amount of academic progress their students make from one year to the next. Often known as “value added” ...

How good is one teacher compared with another? A growing number of school districts have adopted a system called value-added modeling to answer that question, provoking battles from Washington to Los ...