I wrote a whole bunch of stuff about how the PSAT was not a good test for a 3rd grader before I Googled NUMATS EXPLORE. NUMATS used to use ACT's EXPLORE test, an 8th grade level test, as an above-level test for 3rd-6th grade students.

EXPLORE is no longer offered by ACT. NUMATS now uses PSAT 8/9, which is different from the PSAT that HS juniors take. It looks like it would be an appropriate replacement for the EXPLORE.