Thank you for all the feedback. It is great to find other who have faced a similar dilemma.

We have made several decisions about my sons education without giving him a choice.. In this case he feels the fifth grade kids will pick on him. He has seen that sort of bullying at school before. It could be he is overreacting since he is pretty sensitive (especially about being different).

The principal told me again today that she will not "create a special curriculum" for him is he stays in 4th grade. He can stay in 4th or move to 5th. She advised against letting him work ahead in math if he stays in 4th. Pretty discouraging. I (nicely) let her know that he will work ahead to his heart's content.

My preference is to have him accelerated by subject but stay in 4th. My next stop is to have another discussion with the district to make sure I understand all the options. It seems unbelievable that he is the only kid in this district in this situation. This is th Boulder Valley School District, by the way.

Thanks again, and I hope this thread is useful to others..