There's some more information about it here: http://www.crmvet.org/nars/schwartz.htm#corelittest :

Then the test — and how it was graded and administered — got even more insidious. Check out question 21. It says: "Spell backwards, forwards". If a Black person spelled "backwards" but omitted the comma, he/she would be flunked. If a Black person spelled "backwards," he/she would be flunked. If a Black person asked why, he/she would be told either "you forgot the comma," or "you shouldn't have included the comma," or "you should have spelled 'backwards, forwards'". Any plausible response by a white person would be accepted, and so would any implausible response.