I teach at my second grade son's school (moved there this year for multiple reasons). I only mention this because while it does help things, it also complicates this a bit.
My son has always been ahead of the curve developmentally where "academics" are concerned . . . we knew early on that something was "different" when he started talking at 6 months and could read sight words after he spelled with them wooded alphabet letters well before 2. He has always had an natural love for learning and exploring and once he started school that only continued.
In Kinder, I didn't push for much additional differentiation because we felt that he had plenty to learn in terms social and physical development and he was in a good place.
In first grade, he had the same teacher. We were initially excited because she knew him so well and we were hopeful that it meant good things for him. She really didn't differentiate much, despite the obvious need. We had amicable conversations about it which improved things a little, but in the end I was highly disappointed. (There is no GT program for students in K-2 in our school. Sadly.)
This year he was in second grade. His teacher is a PHENOM. She "gets it" . . . she differentiates, she challenges, she inspires, she sparks imagination and motivation and is just fabulous!!
She came to me on the second day of school saying that she couldn't believe what she was seeing. She continued to challenge him in ways that were really exciting, but also a lot of work . . . and while I, as a teacher and a parent, definitely believe that it is any teacher's job to DO that work, I also know the challenge of finding the time to do it right when a student is so far above grade level.
Fast forward a month . . . she came to be recommending that we move him to third grade. Our principal was supportive, but also cautious, which was fine with me. We ended up leaving him in his second grade room for all but math and reading.
He joined a third grade class for math and reading in March. (I was disappointed that it took so long, but sometimes finding the balance necessitates a little give on both sides . . . so hubby and I rolled with the punches knowing he was in a great place in second grade anyway.)
Third grade hasn't been anything of a challenge for him. We didn't necessarily expect that, but felt it was a good way to keep him moving forward, knowing the plan was for him to go into fourth grade the following year.
Fast forward a little more . . . his third grade teacher is anything but great.
I've tried to be respectful in my summation of her, knowing I am also a teacher and wanting to be fair before jumping to conclusions, but . . . it is worksheet, worksheet, worksheet and she doesn't differentiate ANYTHING. Even worse, she doesn't seem to TEACH outside of the curriculum / worksheets at all.
My son, like many of yours I suspect, has long had things come really, really easy to him. Having to slow down and work when things are more complicated (multi-digit multiplication, for example . . . he knows it 100%, but because there are so many steps he'll often just fly through it skipping steps that he CAN do in his head, but then will write down an incorrect number somewhere because he's doing too fast . . . he just hasn't had to learn to work methodically. I know he'll be fine in the long run, but my biggest fear all along has been him not learning to WORK for or THINK about things) has been a challenge for him.
He's at the very top of her third grade class (and while it isn't a competition, he scored higher on the NWEAs than any third grader in our school and the vast majority of fourth graders and fifth graders too . . . he can perform).
She recently told his second grade teacher (who told me with good intentions, but know I'm fuming) that she "doesn't think he's gifted . . . he doesn't put effort into anything . . ." and she completely bashed a story that he wrote in her class.
She didn't provide a rubric or ANY expectations for the story. She told them to "write a fantasy story that they will later illustrate" . . . that's it. I even asked her what the assignment was because I was shocked when that was all he told me . . . and he was right.
So my newly 8 year old who hasn't been taught to write, but has picked it up from all the reading he does (obviously in K / 1 / early 2 he learned sentence writing and basic paragraph writing, but at that level it is uber-basic) wrote a long story that his second grade teacher was jumping for joy over. (I haven't seen it yet.) She was incredibly impressed and couldn't wait to see what third grade teacher had to say about it.
She trashed it. Not in front of him, but to his second grade teacher. There has been issue after issue . . . and this has put me over the edge.
She threw out an oral assignment to her entire class with no rubric, no goal, no expectation, and expected my son to write something over and above everyone else . . . because he's "gifted" (he has now taken the appropriate tests, yadda yadda yadda, so he's officially in the program for next year; she isn't the gifted teacher . . . which makes me wonder why he was placed with her anyway, but . . .).
She seems to think that he should naturally know how to do everything and if he doesn't perform to her expectations, he doesn't belong there.
I'm heartsick. I'm furious. I just want him OUT. He has started to dread that part of school. He was sick for a week and the huge stack of worksheets (on many of the same topics) was enough to make ME crazy . . . he was going stir-crazy doing the same work that he had already mastered over and over again. I finally pared down the work, making sure he "proved himself" on one of everything and called it good. She didn't say anything to him or to me and I chose not to say anything to her either.
I want her to know that she has sucked the love of learning out of him while she berates him (not to him, but to his second grade teacher who was equally upset as I am) for not meeting her expectations without knowing what they were. This woman should not be in our profession. She seriously embarrasses me as a teacher.
I guess I don't know what I'm looking for. Thoughts? My husband is in full support of pulling him. We have only 8 days left of school anyway . . . but I also don't want to send the wrong message to my son. I want him to know that we can't just quit things because they don't go our way, yet I know he'd find some of his spark again if he could just stay with his second grade teacher.
Reading that, it really is no contest, isn't it? He needs to be done with this third grade teacher. He isn't sure about going directly to fourth grade next year (where he'll have a GREAT teacher in the GT program), so having a third grade classroom (the GT teacher, not his current) and going to fourth for math and reading is an option (thanks to our supportive principal).
This got long. I'm sorry. I'm just furious and sad for him and wish I could go to her and make it clear that the issues in her room have little to do with him (a newly 8 year old kid who can write pages and pages of fantasy story from his own creative mind with solid sentences and paragraphs not having been taught a thing about it . . . it was better than most of my fourth graders' work) and more to do with her teaching style. I just don't want to sound like the furious mama lion that i am, I guess . . . ugh.
Thank for reading. Any thoughts are appreciated. I never imagined the struggles we'd have being on this end . . .
), but with her lack of direction, differentiation, and inspiration. 
I would just be wary that while pulling him out makes sense to you, your principal or your co-workers might potentially see it in a different light. It's clear you want to see change for gifted students at your school, and you're going to be in a good position to do so next year - so I wouldn't want to leave an impression with any of your co-workers that you'll want to have on your "team" next year thinking you are quick to react impulsively or give the impression that you are judgmental of other teachers.