Any kid can have a bad day test-wise. It can be hard to pin down what skewed the results. It might be the test admin, but it could also be low blood sugar, minor illness, stress, or being over tired. Sometimes it's a combination effect. Young children are particularly likely to have trouble "showing what they know" on a test that may take several hours.
I'd suggest that you try again in another year, with a different test admin. If you do retest, be aware that there are rules about how often you can use the same instrument for an individual.
