I feel this is a complex issue - I was certainly one of the 'privileged' children in this regard, and much of my practice was in taking tests rather than on the test material, which I could certainly have done without. At the same time, I think the ability to perform complex cognitive tasks under high pressure is an extraordinarily useful aptitude - while I'd be all for less and less standardized testing, perhaps some resources should also be devoted to learning how an economically disadvantaged child can be helped to excel at cognitive challenges under pressure.