In our school district they give CoGat to all second graders ostensibly to help teachers understand the kids' relative strengths and weaknesses. It is paid for out of the gt budget so I strongly suspect that they are searching for kids that didn't opt for the voluntary testing.
If it is being used as a gifted screener, you may want to call your district's gt department and explain your concerns. I vaguely remember a presentation by our gt department where a "slow" (speed-wise) kid only answered half of the questions but got them all correct. This triggered the department to recommend the kid for further testing with a different assessment, Ravens? KBIT? that might give better info than the CoGat.
I don't think it is being used as a gifted screener at this point (but I'm sure if a kid qualifies they can apply for the program). The principal said it is to see how the kids are doing. My concern is that she will not comprehend correctly the questions due to her dyslexia and get answers wrong b/c of it so it wouldn't be an accurate depiction of her ability. She also can work slowly and probably won't do as well if it is timed. And lastly, I have heard on here about how some don't like the cogat and their kids just don't do as well on it.
