Hmm. Could be the WRAT-4, which is fairly short, and can be administered to groups. If so, it is moderately reliable. It's a favorite of neuropsychs, because of its brevity. Some of the gifted screeners also include a brief achievement screening test, so it could be one of those, too. Not quite as reliable.
Other than the KTEA and WIAT, other achievement tests include the WJ and PIAT. Then, for math specifically (not a comprehensive), the KeyMath and the CMAT. These latter two are more in-depth than any of the comprehensives, but (curiously) neither one includes fluency measures. Not that should matter for this particular function.
Personally, I would want to see how students performed on a series of unit assessments in the actual curriculum, as a predictor of success in accelerated math, rather than performance on instruments designed to determine rank-order against the national norm group. One can hope that there is a placement test for the destination curriculum.
