Does growth model measure up to Indiana law?

There’s a lot to be said for the Indiana Growth Model, the statistical method that Indiana uses to calculate year-to-year student growth on math and English test scores. It’s far from perfect, but it’s a much better measure of how schools are doing than looking at how many students pass the tests.

It may be a challenge, though, to use the model while complying with a state law that says Indiana must measure students’ growth in relation to their proficiency on state standards.

That’s especially true now that Indiana has adopted new “college and career ready” standards and will be giving a new version of the ISTEP+ exams, aligned with the new standards, in the spring of 2015. Is it possible to measure growth in proficiency when you give a test for the first time?

The law in question is House Enrolled Act 1427, adopted in 2013. It says accountability measures “must be based on measurement of individual student academic performance and growth to proficiency” and “may not be based on a measurement of student performance or growth compared with peers.”

But the State Board of Education voted this month to use the growth model in 2015. Indiana’s Center for Education and Career Innovation and the state Department of Education recommended the approval.

CECI and DOE staff cited an analysis by testing expert Damian Betebenner, who helped design the Indiana Growth Model and advises the state. He suggests using a statistical adjustment called “equi-percentile concordance” to correlate the 2014 test with the new, 2015 test. That, he says, will make it possible to keep using the growth model to measure students’ test-score gains.

But his report to the board also says that, with the move to new ISTEP+ exams, it won’t be possible to evaluate students’ gains or losses on a single test from one year to the next. “Without gains/losses,” he writes, “growth must be calculated using norm-based metrics that compare like students as they progress from the ISTEP+ to the Career and College Ready Assessment.” (Italics added). Continue reading

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