I feel for people who want to measure how their kids are doing! It can seem important to see their test results, to reassure ourselves that they are learning what they should know.
On the other hand, as a test-giver for low these many years, I recognize that many variables influence testing. The student's mood, their confidence, their skills, the relevance of test questions, the motivation, the ability to withstand pressure, and even the time of day can all affect how students do on a test.
I used to take reading scores as gospel, but I've found that reading, especially, is very difficult to measure productively. Someone's background in the area read is crucial. I used to do demos for teachers where I showed them a "college" level text and asked them questions. In some areas, they could read at a college level, but in unfamiliar areas (such as nuclear physics) the same reading level seemed incomprehensible. Why should our kids be any different? When people say there is a racial gap, couldn't it possibly be partly because of the subject matter and the background of the students? If so, isn't it the TEST that is partly at fault? It makes testers immensely powerful if they can determine the types of questions that are defined as "good" reading levels. Do we want to give them all that power? People used to say that tests were biased- what happened to that concept? Now they just call the teaching bad.
I wish I could teach in a democratic school where only the STUDENTS could decide when and what they would test on. Let's try to develop more of these. It would disempower the testers and empower students instead. A much more worthwhile endeavor!