As I have noted, denying racism has an evidence problem. But those who persist in denying the impact of poverty also have an evidence problem; thus, they have to manufacture evidence.
But manufacture evidence they will—as evidenced by Hanushek, Peterson and Woessmann (2014). However, David Berliner and Stephen Krashen have now unmasked that effort:
David Berliner Responds to Economists Who Discount Role of Child Poverty
Do American Rich Kids do Worse on International Tests than Rich Kids from Other Countries?
I also recommend this, related:
dr. p.l. (paul) thomas 
One of the most interesting articles on the long term effects of being born poor that I have ever read is “The Poverty Clinic” by Paul Tough, published in The New Yorker, March 21, 2011. (I know some people just don’t like Paul Tough, but this article is worth reading). It makes a strong link from the ACE study, which established that multiple adverse experiences in childhood directly effected physical health in middle age (no mediating variables, that could be considered “bad choices” needed)back to what we know about the effects of stress on the developing infant brain. The doctor who is the focus of the article gives one of the best descriptions of the causes of the achievement gap I have ever seen, and the article makes it clear that if we are going to overcome the effects of poverty we need massive, coordinated medical, social and educational interventions from a very early age. Expensive, yes. But as a nation can we afford to just lose children? I’m afraid a lot of people think we can.
Of course, we could begin by raising the minimum wage …