Flugelr, I disagree ; the fact is, lots of Africans speak all sorts of different tribal languages anyway, 3, 4, 5 or more, including supposed "enemy" tribes. I recall the story of a relative who visited Kenya, where two girls went through about 4 different languages so that they could find one with which to bi.tch about a third girl who didn't understand. Similarly, in the early middle ages [1000-1300], many lessons in Britain were taught either in French or Latin because English was seen as "vulgar". When lessons were taught in English, I highly doubt that this reinforced differences with France - if anything, it alleviated them, as people [well, the rich] were no longer subjected to the "yoke" of learning French for education.
There have also been some convincing posts earlier, but I'm afraid I can't recall them exactly.