Nevermind; I figured out what the problem was. I've always used plain simple notepad for editing EDU stats but as bovi pointed out in a FAQ thread that won't work for some of the other files.

Another question then: is it actually necessary to make the other available ethnicities "antitraits"? I did so because I thought that would prevent adopted characters and suitors from getting double ethnicities, but it doesn't do so - only adding a "ethnodetermined" trigger will do that.