Don't panic! The most likely explanation is that it's one of these confusing reports you have in the US where what it means is not that he is working like a 9th grader, but that on this test of 3rd grade material he did as well as a 9th grader tested on the 3rd grade material would probably do. Does that make sense given your knowledge of what test it was? I'm sure someone here knows specifics of the test if you don't.

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