I am surprised that no one has pointed out how most IQ tests have built in bias . This is unintentional and is hard to negate. The tests often test not intellectual potential ,but what has already been learned. Take a look at what Prof. Martin Shapiro of Emory University, says.
According to other research, items which facilitate ranking and sorting are often items which, perhaps unintentionally, factor non-school learning and social background into the questions. Such items help create consistency in test results, but they often are based on the experiences of white middle-to-upper class children, who also typically have access to a stronger academic education.
For in depth information on this please read the following
http://fairtest.org/racial-bias-built-tests
http://www.theneuroethicsblog.com/2013/09/intelligence-testing-accurate-or.html