I also read the page in the PDF you linked that was the source of the table and became more confused, because it very clearly writes out that:
>What this means is that 40% of the variation in students’ SAT/ACT scores is attributable to differences in socioeconomic circumstance.
I think you are either:
1. Misunderstanding correlation coefficients. Correlation coefficients range from -1 to +1, implying a 100% negative or positive correlation. 0.4 and -0.4 are moderately positive and negative correlation values. That table is saying that if you are an underrepresented minority, you are expected to do 40% worse on the SAT/ACT.
2. Quibbling over the "thing that correlates highest with SAT score" claim, because you feel like 0.4 is not high enough of a number. The only factors with higher correlation values than 0.4 in SAT/ACT scores would be stuff like "Was the student currently injured?" or "Did the student make it to the testing center?"