I am struggling with the same kind of issues as several have posted but we are a few years farther along so finally arranged private testing for DD9 (HG), scheduled for next month.
I first noticed the typical letter reversals in K and 1st grade and heard the same comments about normal first grade issues. This with a student reading around 3rd grade level in early 1st. In retrospect I noticed that she tended to be a whole word reader and struggled using phonics to sound out new words. DD skipped 2nd and went to 3rd successfully, remaining in the top 5-10% of the class. I still saw occasional letter and number (usually 3s) reversals, but not frequent.
Got to 4th grade and noticed that she would ace spelling tests, but then not be able to spell the same words in writing activities a few weeks later. She was reading fluently, still assessed about 2 grade levels above grade. But I started to notice difficulty in reading aloud - she would skip or replace words, struggle with sounding out and pronouncing words that she was capable of using in conversation. None of this was what I would consider frequent, but enough that I noticed. She stuggled with the increased writing requirements in 4th grade, also. She couldn't write as fast, which usually meant she didn't write as much.
Since 4th grade she had complained of vision problems; visits to the regular eye doctor showed no problems, but based on her insistence the Dr. finally prescribed minimum reading glasses, which she uses consistently. Now we are in 5th and still every once in a while I see the number reversals. Still struggles somewhat with spelling, still struggles with the writing, especially keeping up with the class, taking notes, copying the schedule, etc.. She seems to do fine with reading comprehension and vocabulary, but really seems to have difficulty with making inferences from reading. We can discuss any book she has read for pleasure and she can relate specific scenes as well as character motivation and plot points, etc, but reading short passages from the school curriculum and making inferences in a test/assessment context is kinda hit or miss.
It was hard to make the decision to move forward with the testing, since this doesn't really look like a problem, but something is not quite right. I'm just not sure how much of this might just be developmentally normal, which is why I've waited so long. After discussing with the psych who will do the testing I decided to go ahead and do the testing now, rather than waiting to see if it gets worse. The advice I got from the psych is that middle school is often the place where she sees these types of issues really manifest in the HG/2E students. That is the point where the instructional materials become too dense to pick up context cues that they rely on in other types of reading. Prior to this point some of these students camouflage these difficulties by working around them but it becomes more difficult the further they go in school. I figured I'd rather know sooner than later since it's so much harder to recover once things go downhill than it is to prevent falling off the cliff in the first place.
I didn't even try going through the school though, because I'm sure they don't see a problem - she is still in the top 5-10% in her grade, reading 2+ grade levels ahead, and actually seems to have a good teacher fit this year. Besides as reluctant as they were about the acceleration, I'm not interested in giving them anything they could use for an "I told you so" moment. So I sypmathize a lot with you and the other posters about the concern that school doesn't think anything is wrong.
Just a little perspective from later down the road. Not that I have any answers yet.
