Trying hard isn't enough to overcome stereotype threat

[At Berkeley, math professor Philip Uri Treisman] saw black students—in an effort to succeed where their abilities are negatively stereotyped—following a strategy of intense, isolated effort, a strategy that often set them up for defeats and discouragements. They were trying hard, they were taking my father's advice (and probably their own father's advice), but they were trying to do it all by themselves, in a class where other people were working more happily and efficiently together, pooling their intellectual resources. 

Claude Steele, Whistling Vivaldi: And Other Clues to How Stereotypes Affect Us (New York: W. W. Norton & Co., 2010), p. 103

People experiencing stereotype threat are already trying hard. They're identified with their performance. They have motivation. It's the extra ghost slashing that is in their way.

Id.,  p. 112