if you're black you need higher test scores and grades to qualify
This seems to me mistaken. The reason race can be used as a proxy in the first place is that there is some correlation with performance on the standard tests. If you use the standard tests, then that entirely screens out all the race information; there is no additional information in race that you didn't get from the test. This is similar to checking whether the plane flies: All information from authority and from theory is screened out by the experiment.
More generally: If A is a proxy for B, and you use B, then trying to use A in addition is double-counting.
Now, perhaps you are arguing that race is a proxy for test scores and something else, and you can still extract the something-else? If so this should be made explicit.
Consider a test followed by a re-test (which we are trying to predict). To calculate expected score on the re-test you need to apply regression to the mean. For a population where you measured lower mean or (in high range) smaller variance, you'll have to regress more.
Of course, that mathematical fact doesn't make it non racist or morally right to do such adjustment. You could add a couple simple extra questions to the test, to obtain similar improvement in the accuracy. Or you could use some other side data instead - weight, height, and blood type, for ex...
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