African Americans were often forced to attend sub-par schools or even prevented from seeking an education entirely. This was a way of keeping White-control of the former Confederate states. Now, instead of literacy tests, we have voter identification laws.
[This] Louisiana “literacy” test, singular among its fellows, has nothing to do with citizenship. Designed to put the applicant through mental contortions, the test's questions are often confusingly worded. If some of them seem unanswerable, that effect was intentional. The (white) registrar would be the ultimate judge of whether an answer was correct.