I once knew a boy who has made to memorize some surahs from the Qur'an from listening to Yusuf Ali's translation on audio tape. And he was made to recite what he had memorized in a tajweed class (of all places, right?) to an imam who was shocked and tried to explain to the boy's parent why this was not a good idea.
Presumably, the intention was that the boy would learn the text in meaning this way, rather than "just" a text which he wouldn't be able to fully understand. But a translation is not equivalent to the Qur'an. Having spent the last few weeks reading the Qur'an in Arabic and trying to discern the meaning from it without relying on an English translation has taught me to appreciate the difference, and what is lost through translation.
But think of a community that doesn't have the ability to understand to Arabic. Without it, they might lose even the appreciation of the Arabic and place more value on the translation, even to the point that they would memorize it as though it were the words of Allah.
We're supposed to have a relationship with the Qur'an but how can we if we can't even understand it? We shouldn't let children grow up without at least a basic understanding of Arabic. Because without Arabic, as a community we lose the Qur'an.