Tough question.
From what I read, he's being provided with a lot of interesting stuff, but it's all outside the classroom. The problem seems to be inside the classroom. The school day is a long time to sit around not doing anything productive.
I'm not convinced that extra stuff at 4 pm can alleviate boredom at 11 am. In fact, the boredom is probably highlighted because he knows exactly what he's missing. So I suggest focusing on what the school can do to help.
What do you see as the liabilities of a grade skip now? How will they disappear or be attenuated in middle school? How bad is the boredom now, and what will be the effects of two more years of it? For example, how will too-easy material affect his ability to study more difficult material later? etc. etc.
Val
