This is explained in an excellent article by Jonathan Keiler in Education Week, When test scores become a commodity (subscription only article, some of it is quoted on Will Richardson's blogg). He argues that test scores have become commodities and trading is therefore not always honest. Since schools are paid by results and good results enhance reputations there is a great temptation for some to sugar the results to increase income and prestige. Teachers are judged as good if their students pass the tests and this can result in teaching the test. Competition between schools and between teachers means less collaboration and less sharing of resources. This in turn leads to everyone having to reinvent the wheel over and over again. The students may pass the tests but have they really learnt anything? Teachers who don't focus on tests risk being seen as incompetent. The result is a test factory that has little to do with producing the critical independent thinkers and innovative entrepreneurs that industry keeps asking for from the education system.
Schools could become little more than test-preparation institutes, ignoring subjects and skills that are not assessed, with faculty members who resent and distrust one another. Meanwhile, many honest and dutiful teachers will go down in flames.
Then there is the matter of student cheating. Keiler argues that the commodity approach invites this since test results become hard currency and when a commodity is valuable there will always be people tryig to cheat the system to earn a fast buck or two. That happens in most areas of society and it is no wonder that it also occurs in education.
Related to this is an article in the Washington Post, School board member who took standardized test, about a senior school board member who decided to try the tests that his school students had to sit. He failed spectacularly of course but his criticism and insight afterwards are interesting:
“It seems to me something is seriously wrong. I have a bachelor of science degree, two masters degrees, and 15 credit hours toward a doctorate. I help oversee an organization with 22,000 employees and a $3 billion operations and capital budget, and am able to make sense of complex data related to those responsibilities....
It might be argued that I’ve been out of school too long, that if I’d actually been in the 10th grade prior to taking the test, the material would have been fresh. But doesn’t that miss the point? A test that can determine a student’s future life chances should surely relate in some practical way to the requirements of life. I can’t see how that could possibly be true of the test I took.”
I'm not against testing. We all need challenges and ways of tesing our skills in realistic situations and we thrive on a certain level of competition. We need to focus on what and how we test so that students' futures are not simply decided by how they perform in an exam hall. There are plenty of excellent examples of meaningful assessment and examination but the debate keeps veering back to simplistic views of assessment and an unfortunate association between education and the market place.