When he complained in the classroom, his teacher told him that the other kids need to catch up.
It sounds like your school system is 'of 2 minds' when it comes to meeting the needs of kids who already have mastered 'the basics.' The fact that they even use MAP testing, and then that they look at the results and made changes in his Math worksheets is a very positive sign. In some ways your district is far ahead of other districts.
Then there is your son's teacher's attitude. It is a lot to ask each teacher to teach such a diversity of readiness levels in a single classroom, and I like your idea of moving the child physically into a room where there will be 'enough' children at the same readiness level to justify teaching them. If the school balks about it - tell them what the teacher said above and see if they stand behind that perspective.
I would also see how quickly you can get yourself an appointment to visit the school and see what the 'gifted program' consists of. Gifted programing can vary from a classroom where each child works at their readiness level all day every day no matter how far 'ahead' they are, to 20 minutes of 'indoor camp' a week where the kids enjoy each other's company while solving Sokudo Puzzles.
The range in between is absolutely dazzling. So go observe and see what sort of gifted program is availible. If the gifted program has a 'math class' then perhaps that would be the best place for you son to do subject acceleration into.
If the school will tell you, ask 'how many other children in my son's current class are within 5 RIT points of my son's English and Math.' Then you can point out how fruitless it is to try to differentiate for just one child, if in fact, he is the only child in the classroom. What I like about RIT levels and MAP is that it's all about 'what does this child know and what are the next learning goals for this child.'
It take the questions of 'what is wrong with your school?' and 'who is smarter than who' and 'what did you do to make your kid so much smarter' totally off the table. Which is where they belong. The only thing that belongs on the table - in my opinion - is: What are the child's needs, including educational needs, what possible resources exist to meet those needs and how can we best connect the two.
In my observation, it doesn't have to be perfect, but every improvement at school makes a very large improvement in the child's overall daily life.
Welcome kjayne1! So very glad you found us!
Grinity