When a member of a group is primed with a stereotype that their group underperforms at a task, they are more likely to underperform. So there could be a selection process biased against a group, and a selected member could be an above-average performer otherwise but, because of work environment, be underperforming.
Some universities work to remedy this through support groups or other practices aimed at under-represented minorities, and they appear to help students be more successful academically. On the other hand, there's the Hawthorne effect... https://en.wikipedia.org/wiki/Hawthorne_effect