An ACT score is ~98.5% of all test takers. In other words, only about 1.5% of all test taker score 33 or better. To be at 30%, that HS must do more than 20 times better than the national average. Statistically, that is definitely an outlier (>3 StDev out) of the whole test taking population. Of course, this could happen if only the top portion of the HS student body took the test. Without knowing how many students took the test, I don't think these numbers mean much.
At least we know now that it is not 30 ~ 40% of the 1200+ student.
I said I ate 太多了一点 because, whether it is 30% or 3%, it does not really matter to me at all. Just like if some one is really professional pop star or she could not carry a tune in a bucket.