Our son did quite well on the SCAT the first time (4th/5th Grade) -- in line with our expectations -- and qualified for CTY programs (95% in math).
He took it again last year to qualify for the next level of CTY summer program and scored considerably lower -- especially on the math portion (63% in math) and failed to qualify.
As it turns out, the real issue was not a lack of understanding -- he is just not focused enough on accuracy during testing.
For the SCAT math in particular, when he was finished, I took a peek at his scratch paper (provided by testing site) and it was essentially blank. He felt he could do everything in his head... and his score showed how wrong he was!
We've been working on "test-taking" the last few months and he's definitely upped his game, although nowhere near where it could/should be.
In reviewing his tests & quizzes for the last several months, all mistakes (except one) were careless. He knows the material inside & out and when forced to take his time + show all the steps, he nails it. But as a test-taker, he is still developing.
He took the SAT at the beginning of June and hit the necessary marks -- so at least the CTY qualification is behind him.
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ALSO... maybe he could try re-testing on the SCAT? Or take the STB or one of the other tests offered through JHU?