For all the discussion on standardized testing treating learners equitably, there's tremendous evidence to the contrary. In fact, we're seeing evidence of this in many colleges no longer using SAT scores as criteria for admission. 

Many of these tests are designed to weed learners out. And there is a whole industry around test prep materials for these tests in to help learners become one of the few who get a high enough score on these tests to help them get admitted to the program of their choice. To be able to use these tools to prepare for the test, you have to have both money and time, so they're much less accessible to people with lower incomes.

Combine that industry with the sheer difficulty of the tests and you've got another system just reinforcing inequality.