"Believing we can improve schooling with more tests is like believing you can make yourself grow taller by measuring your height."
It's catchy, but it's not quite true.
The problem is that testing produces feedback which is used to modify the educational approach. No-one wants to be responsible for a generation that failed, so no-one is willing to experiment, instead they try to do what will 'work' and what will 'improve' results, when in reality we can't predict what will work.
Testing is part of the scientific method, and an equally important part of that method is a willingness to fail in the pursuit of knowledge.