Here is my response as a teacher in Minnesota. Do I like the tests? Not necessarily. I hate how much time is put into them. Thankfully I don't teach in a school that takes two weeks away from the curriculum to teach how to take the test like some schools do. But in my building alone, which is a small building, we have 14 days when the computer lab is off limits to everyone because of state testing. Plus we have a district test that K-5 take that adds at least another 14 days without access to the lab. As a reading intervention teacher that also means that during those 28+ days at least some if not all of my small intervention groups are cancelled. That is a lot of lost teaching time.
Is the information from the tests valuable to parents? Not so much. My husband who doesn't have an education background doesn't get it at all with our own kids. I pay a little more attention to it.
Is the information from the tests valuable to teachers? Yes and no. We don't typically get the test results from the state tests back until after the school year is over. Sometimes not even until the new year has started. That limits how we can use the results in some ways. The district test we get data back immediately. We use that data throughout the year to look at changes we need to make in curriculum and instruction. We use it as one piece of data in determining if students need interventions or would qualify for special Ed. But, it is just one piece of information. We never base a decision on just one test score. We realize that some kids just don't test well. We realize that the test is just one snapshot of that student's performance at one specific time. It may not be 100% accurate. Even the best student/best test taker is going to bomb the test if if their grandfather or even if their dog died the night before. A kid isn't going to perform as well if he/she was up late the night before because baby brother screamed all night or woke up too late to eat breakfast. There are lots of factors that can affect test scores. I remember taking a standardized test in a really hot room one time. I did not perform well because I was so uncomfortably hot that I couldn't concentrate.
Some school districts base a lot on test scores--including teacher pay and performance evaluations. I don't think I could ever teach in a district like that. Yes, the scores are important, but they are just a snapshot. They aren't all encompassing.
Yes, the test scores will become a part of your child's cumulative record. But in all honesty, probably the only person who will really look at her 3rd grade score after she leaves 3rd grade will be her 4th grade teacher. And maybe intervention teachers if there seems to be a need (reading or math intervention, special ed, gifted and talented, etc.).
If your school's curriculum is aligned with the state standards that the test is based on, yes the results will be a good representation of how much your child is learning. But also keep in mind that many times the test has been developed by people who are not involved in the field of education at all. Sometimes the questions are "tricky". Sometimes the tests are written to find out what kids have not learned instead of what they have learned. Every state is different.
Personally, I think people get too stressed out about the tests. But, I don't teach in a high stakes state. I don't have to worry about losing my job if my students don't score high enough. You can find some pretty fun videos that teachers have made to show kids before testing. I remember seeing a pretty funny parody of "Let it Go".
As a teacher, my suggestion to parents is to not talk negative about the test. If you seem stressed about it, your child will pick up on that. Most kids who go into a testing situation stressed don't do as well. Get a good night sleep the day before. Eat a good breakfast. Most importantly, let your child know that you don't really care how well she does on the test, because you know she is an awesome kid and you don't need a test score to show you that. Don't reward good scores or punish bad scores. In the long run, the scores don't mean anything. But, if you are concerned about the result, don't hesitate to ask the teacher if the test score mirrors what your daughter does on a day-to-day basis. Just remember that it is one moment in time. You wouldn't want someone to judge you as a mother based on that one time you took your kid to a play date with dirty clothes and uncombed hair.