From what I've read, the CAT is one of the easier tests. The ITBS is supposed to be a bit more challenging and "if you really want to know what your DC knows" use the SAT/10. Now I put that in quotes b/c that is what someone said at the WTM boards. We may do the SAT/10 this year. I think I've seen the recommedation to keep testing up a level until child reaches 50th%.
The SAT/x was criticized in the 1988 Lake Woebegone effect report on how all 50 States score above the national average. As I remember from the paper, the test was normed once on a small, less than average group of students (in TX, I think). That test version and norms were then apparently used for almost a decade which nearly ensured any school district could come out above average. I don�t know how the current version is generally viewed by watchdogs today, but it is still favored by many school districts as the back-up achievement proof to state tests.
I think the ITBS is renormed continually and since it is used by private, homeschools and a good portion of public schools it should have fairly accurate percentile yields.
