I'm not in CA so I can't give you specific advice, but fwiw, I'd check to see which achievement test is most commonly used in your school district (WJ-III vs WIAT) - when advocating, it's so much easier to be working with a set of tests that teachers and school staff are familiar with. The testing folks at the University might have a good idea which is used by your school, but to be safe I'd check with the school first.
The WIAT might be useful if you had the same psych test because (I suspect) she could draw conclusions based on the relationship of WIAT subtests to WISC (you can do the same thing for students who take the WJ-III Cognitive with the WJ-III Achievement test - we've had this for each of our children on the WJ-III and the report that relates the ability to achievement was helpful in a more meaningful way than the evals where they've had WISC for ability and WJ-III Achievement.
Re the CAT-5 I am not sure - it depends on what you're trying to use the testing for, what you need to get there, and what other achiievement testing you have.
Best wishes,
polarbear
