Most high–stakes tests are summative—they attempt to sum up what's been learned, and then apply good or bad consequences for students and schools based on that judgment.
There's a lot to be said for summative tests. They provide a snapshot of a school system, can be easily compared to prior years, and currently form the basis of accountability systems that ensure schools are effectively teaching all their students. However, summative tests are not perfect. First, they do nothing to identify and remedy instructional problems before they become critical. Even for material taught in October, results are generally not available before the end of the school year, so they're of no use to a teacher seeking to help her class with problems they're experiencing right now. Secondly, having one big test makes everyone anxious, and is disruptive to school life.
The tests and quizzes that teachers have traditionally given throughout the school year are formative—they help inform instruction, usually in a low–stakes way. Most formative testing is not consistent or reliable enough to be used for high–stakes decisions (which is why even traditional final exams count for only a portion of a students' course grade), let alone to look across classes or schools.
Neither formative nor summative testing alone can meet the needs and responsibilities of public schools. We'd like to see a hybrid of low–stakes, ongoing, formative (also known as "interim") assessment that guides teaching and learning, tied tightly to both the curriculum and the state's high–stakes summative test. This, in fact, is the use–model of Assessment Center, our formative testing tool. Our hope is that over time it will be possible for many of the judgments (e.g. mandatory summer school or other instructional interventions) that now emerge from high–stress, high–stakes tests to be made on the basis of a sophisticated formative accountability system. The goal, of course, is to create a formative or interim program that can identify and help to avert these negative outcomes before they happen, for as many students as possible.