Why is educational policy being made based on standardized tests, where data could easily be erroneous?

As a teacher, I dislike standardized tests! However, it is the only way to really compare students to see where they are, and to measure how each teacher is supposedly sticking to the state adopted curriculum. There are a lot of flaws with the testing, and it is definitly biased based on social cl and resources. As for as alternatives goes, it hard to see what could replace it. But if anthing comes along, I would definitly support it.