Let's put it this way-- I'm really looking forward to DD graduating from college next year, since it will finally put an end to this nonsense for once and for all.
DD was, for many years, small for her age in addition to being radically (+3-4y) accelerated, and we definitely live (ideologically, anyway) in Portia's neighborhood, evidently...
We've heard about as much rudeness on this subject as I imagine it is possible to hear. We did our best to not allow DD to hear most of it, but she's like a social antenna, so...
DD came up with one interesting strategy--
give people asking such questions ONE OR THE OTHER-- either her age, if that was what was the important (intended) gist of the query-- or her grade placement in school, if that was the nature of the inquiry. Not BOTH.
Most people really aren't rude enough to pursue asking for the other once they've gotten an answer, and DD was (and is) always truthful.
DD never wanted the attention-- and this kind of social approbation has conditioned her to OMIT her age even when it would be advantageous to her to emphasize her status as a wunderkind (in internships, fellowship applications, in discussing with faculty why she can't actually participate in their psych study for extra credit in class*).
* yeah, yeah-- don't even get me started on the ethics of THAT one, but it's commonplace in psych and ed departments, and let's face it-- a student who is 4-5 years younger than her cohort, and mostly +30 FSIQ points is a built-in outlier in their study anyway. She knows this-- but is still reluctant to offer her age as a reason why she would not sign up to participate (and literally COULD not consent to, legally, until a month ago).
