This week, public elementary school students are sharpening their number-two pencils for the annual state test—the ISAT. In Chicago, school officials have already begun implementing a new way to evaluate results from the exam.

Teachers in tough schools have complained for years that they can take students miles in terms of achievement. But unless kids meet state standards, their school still gets a failing grade. The new “value added” measure will judge teachers and schools on how much kids learn from one year to the next.

MEYER: If we’re trying to figure out what 8^th grade teachers did at a school, let’s look at the growth from the beginning of the year to the end of the year.

Rob Meyer is head of the Value Added Research Center at the University of Wisconsin-Madison, which is contracting with Chicago.

The new measure will also take into account the way family income can affect student performance. Last week Chicago schools chief Ron Huberman said he wants to let parents see how well individual teachers are doing. This measure could help with that.