CoGAT/ITBS is used by almost all local districts here, too, but I have gotten more and more skeptical about it as I watch what happens with kids we know and our program.
My DD's class is a 3-grade split. So kids identified in 3rd are in the class starting in 4th. Kids who aren't identified in 3rd can apply to re-test. Every year there are nearly as many kids entering in 6th as 4th. Why? These kids did not qualify to enter in 4th, and did not qualify to enter in 5th, but qualified to enter in 6th. Every year the class is structued similar to this: 5-4th graders; 9-5th graders; 13-6th graders. Supposedly they take the best-qualified kids regardless of grade, but somehow fail to identify the 13 highest scoring 6th graders when they are in the 4th grade. And there are only ~80 6th graders in the school, so by 6th quite a large percentage of them are in the program.
