I think that epoh has a good point. This is all we've *ever* used in our advocacy for DD.
If you declare yourselves homeschoolers over some summer or long vacation break, for example, you can order inexpensive achievement tests from "Family Learning Organization or F.L.O." and pretty much test any level that you think might be appropriate. We tested only one year out of level before DD entered school (we were in fact homeschoolers at the time) and DD basically hit the ceilings on ever subsection. Straight up 99's.
In other words, we probably (knowing what we know NOW, I mean) could have turned around and jumped up to 4th grade from there to get something that wasn't entirely at the assessment ceiling.
Anyway. That was a CAT-5. The school completely knew what this was and understood that a 6yo who knocked the 2nd grade version out of the park in November was in need of a 3rd grade placement. At a minimum.
In other words, achievement testing may be exactly the route to try if you think that there are no complicating factors (2e) to contend with.
