Just an idea: maybe non-white francophones are immigrants from countries with a different dialect of French, so even if they are technically francophones they have a serious gap in understanding québécois. As French has an extra challenge in math by the way numbers are composed (ex: 80 is literally "4 of 20", not "8 tens") that makes decimal calculations a bit harder than in English, it can skew the results to the observed numbers.