When DS was in 5th grade, he was differentiated in English and subject accelerated (and compacted) in Math.
His teacher knew him from another situation and knew what he was capable of. She was really excited to teach him English and she found books that she wanted to teach him. For example, she gave him an anthology of essays from the founding fathers and had him read them, answer essay questions, and put together a poster on the revolution. This was timed to go with the curriculum that she was doing with the rest of the class. It worked really well.
But the teacher was nervous about her ability to offer math at his level. We were able to work with our state's online charter school and we enrolled him in just the math class. I prepared assignments for him including letting him test out sections he already knew. He did 2 years of math in one year and was ready to start Algebra once he got to middle school. since it was through the charter school, he got credit for the math classes, just through a different school.
Because math has a more set sequence, I felt better about doing acceleration for him in math since we didn't have a teacher who felt that she could give him more depth.
With reading and English, there is so much to read and write, I felt comfortable with letting him explore and go into more depth with his enthusiastic teacher and didn't care that he wasn't officially moving ahead.
I think the key for us was working with the resources that we had, the teacher's strengths, DS's interests etc. There is no cookie-cutter answer. Look at what you have available and what your child's needs are and see if they can be arranged in a way that works for your DC.
