Are there people beyond the classroom teacher that you can appeal to in the school? In our school, the school mission statement includes a section that says that every student has the right to be taught at their own level and in a way that stimulates curiousity and encourages intellectual development. Does your school have any statements like that that you can use to advocate? Also, at our school, the gifted coordinator takes an active role in making sure that advanced students' needs are being met in the classroom even in K,1 and 2 before the gifted program begins. I reached out to her last year when DS was in 2nd and she ultimately started a pull-out math enrichment program (I love her, btw!)for kids not being challenged by regular curriculum.

Maybe there are some additional resources at your school that you could tap in to? The teacher's approach and defense of the review is odd, imo.