Writing a truly good test is not easy or automatic. I agree in principle with the above post in the idea that a good test can be a helpful tool for assessment (and for instruction). The emphasis in standardized testing, however, has not been on the quality of the test. Instead the emphasis has been placed on the scores of students and the "scores" of schools and teachers.
This dynamic leads to a negative situation, in my opinion, where accountability in placed out of order. The test writers need to be held to higher standards so that students, teachers, and schools are being gauged according to a "true measure".
One other, separate point: Standardized testing is used too often. In a 10th grade classroom in California students spend one out of every nine days taking standardized testing. That is too much.
In my opinion, standardized tests should be 1) consolidated so that they are 2) given less often and they should be 3) much shorter for the students.
Some expectations have to be placed on the people scoring these tests. More essays will help to better assess a student's real skills.