This question is based on literacy studies, but it's an issue that anybody from a wide variety of disciplines could weigh in on.
For some demographics, literacy in South Africa is terrible. For example after 3 years of schooling, 99% of isiXhosa speaking learners fail to reach the minimum international reading benchmark. One problem is that there are no normative standards and reading tests against which to measure achievement (e.g. reading speed, reading accuracy etc). But clearly, for this group, if 99% are functionally illiterate, then achievements represent a non-normal distribution (statistically speaking). So how could one ever establish reasonable norms?
Background: what makes this more difficult is that isiXhosa is an agglutinating language (words tend to me much longer) which makes it invalid to attempt to using reading speed standards of English, say.