We have practice state tests this year. They count for nothing, but they are given to students to get them "used to" doing the state tests.
So far, the state tests kind of count for nothing. They are not tied to the teacher's evaluation, they are not tied to funding, they don't go towards gifted program placement. If the school does very poorly as a whole, the school may lose it's charter. But that doesn't look very likely, as they compare to the surrounding public school district. Our school routinely does 20-30 points better than the surrounding district.
Of course, this may change. But I am planning to opt out of the practice tests this year. I also plan on opting out of all state tests until they start to count towards something tangible.
I would not have my children opt out of standardized tests without a strong reason. Teachers' grades are not standardized. Your child may be getting 4's on a 1-4 scale, but you don't know fraction of students are getting 4's. (I think report cards at all level, including college, should provide information about the class distribution of grades.) Scores on state level tests provide comparative information.
My middle child likes working on released MCAS math tests at home, both at his grade level and above. He sees the latter, especially, as a challenge. Each test has a variety of problems, unlike many other tests students take.