I don't really know the answer but I will say this.
I was to all outside appearances a happy kid at school. I did enough to get high marks but not too much to attract attention, deliberately got things wrong in class to "blend in", played sports, had friends, etc. I knew it wasn't ideal but I also knew that A) there weren't any other options or programs and B) my mom made it clear that school was just something you had to do and she wasn't going to advocate for anything special. Even with my DS she has not understood why we would seek an IEP and now a congregated gifted program - "he has to get used to doing boring stuff", "he has to work with a variety of kids, that's how the real world works", etc. It took travelling with us for a month and then an article that happened to appear in her local paper to get her to come around. She was a teacher and had no clue about this stuff.
Anyway, all of that personal baggage to say that I would have LOVED to have had a challenge in school but likely no one would have suspected that. In the end it worked out, I plowed all of my extra time and energy into sports which I still love. I found a great career that is challenging and where I am surrounded by gifted people which I also love.
My DS9 is easy in the sense that it was really obvious that school wasn't working for him so we had to change it. DD6 isn't as obvious. She appears to be like I was as a kid so I face the same questions you are. We're testing her in the fall and hopefully that will give us an idea of what we're dealing with and we can go from there.
All of that probably isn't very useful but you definitely aren't alone.
