Narrowing the test score gap is a worthy goal. We know that many students are left behind and deserve better. But one lesson we've learned from tests already administered is that pressure from parents and citizens provides the best incentives for schools to improve. Simply publicizing the results has already had a substantial effect. At first glance, it also looks sensible to use financial incentives.
Baseball teams rake in the money if they make the playoffs.
Bad teams have financial incentives to improve. But this is where the baseball analogy falls apart. Good teachers are already doing good work. It would be foolish to change what they're doing in order to administer more tests. Teaching to the test not only derails sound teaching practices, but also drives the most creative teachers out of the profession.