I think teachers probably get a bit jaded by every parent thinking their child is amazingly brilliant (which...of course parents think their kids are great!) . But when a child is truly gifted, teachers may think it's the same old 'my child is special' mantra they hear every year.
Yeah. sigh. I think many of us have been there.
DD(then 6) Grade 2:
"I don't think she's as smart as you think she is."
Then, a few months later...
"We pulled her out to do some testing and it looks like you were right after all - she is advanced."
As a teacher, I totally agree with the first part. In some communities, even being just "above average" carries stigma... for the parents. The parents then pass that info along to their kids (a fourth grader should be doing xyz, why is she doing abc and why is he doing qrs) and suddenly the kids go from blissfully doing their thing to worrying and mocking and gloating and acting out and withdrawing and who knows what else.
And then as a parent, I had the exact experience you reported, in three year-old preschool last year. At our first get-to-know-you conference, I tried to explain that he was starting to put sounds together into words, as well as adding, etc., and the teacher just nodded and said "we're working on making sure they really know what the numbers MEAN," implying that we had just had him memorize the phrase "two plus two equals four." Nope, he had figured out adding numbers of objects on his own and we explained subtraction to him shortly thereafter. But yeah, the nodding and smiling.
Fast forward to his spring conference: "I'm going to miss him so much, but am kind of relieved you guys are moving because we've put him through all the four year-old curriculum already, and he's leading THAT bunch. I'm not sure what we'd do with him in preschool for another year. I've never had a kid like him."
It's hard having inside info on both sides of the parent-teacher dynamic. I know what the parents are thinking/saying about the teachers who don't believe them right away, and I know what the teachers are saying about the parents who INSIST that their kid is OMG SO SPECIAL YOU JUST DON'T SEE IT. Both parties get pretty jaded pretty quickly: the parents of the truly exceptional kids who feel like they have to advocate for and prove every little thing, and the teachers who have seen so many cases of parents trying to push their kid into something that's not necessarily appropriate that they have a hard time looking at such things with clear eyes.
I also have a non-show-off-y kid. Ask him to read and he'll read. Ask him to write and he'll write. Ask him to add and he'll add. But don't ask him to do any of these things and he'll just as happily spend his day working on the letter H for the third (YES, THIRD) week in a row and then zooming toy cars around the room. It's the third week of 4K in our new town and I'm nearly 100% certain that he's not even a blip on his teacher's radar at this point. He presents as a "typical" four year-old boy, probably on the active and slightly immature end of the four year-old boy spectrum.
My plan is to let everyone settle in to the school year (they just switched rooms, the teacher is new, etc.) and then take a closer look at things.