I can't imagine why it isn't a requirement. It's not the same as a property requirement or material criteria, and anybody voting who doesn't even know what the offices do or how the government is organized isn't voting on anything butpartisan politics and personality, like the women who voted for Jimmy Carter just because he 'had a nice smile'..
There could be three tests, one each for local, state, and federal, so people could vote in any they pass the test for or all of them. People who aren't up to par can take night classes at any local school, either by paid teachers or qualified volunteers, but using current political science teachers is the best option.
And no foreign languages, just English;; if they don't want to learn to speak the official language, they don't really want to vote. If they're too old or have some other reasonable circumstance, like being a refugee, a real one and not some fake economic parasite just here to steal, some slack can be allowed, I suppose, but their voting would be based on passing citizenship tests anyway, so they are likely to already be up to par anyway. via their studies, , probably more so than many ' natives'.