Ear tags are nice, but more something for Cowgirls I would think. The Ratkin subjugation is currently themed around the colonial concept of évolués, so it wouldn't fit in.
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So "be a good girl, and we'll grant you certain privileges. We may even consider you an equal, if you work hard enough and earn our respect". like how it was done in that African tribe?
If tags were to be a factor, perhaps exceptions would be made for normal classes with one human parent, or for members of a bloodline.
Then again, it could work the other way around, where a tag on your ear is proof of your status, and it warrants respect.