In case you're interested....
Met with teachers and counselors yesterday. I think this is the route we are taking for next fall; my son will go into a grade 5 homeroom (school is 5-8), but take grade 6 math class and maybe ELA too. This is to give him time to adjust to pace and organization to middle school. They will put him on a 504 plan to accommodate the processing speed (it was noted that when given time, he produces well above grade level work, but when time is limited he shuts down and at times produces nothing). We will reassess in December whether or not to merge him into grade 6 mid year and then into grade 7 the following year. The important thing for me was that the school recognizes that they need to change the way they do things to accommodate his learning style and match his intellect. They are even suggesting some online coursework to be done in school to further his enrichment. In the meantime, we are waiting to hear of an opening at a private school known for it's rigorous academics and hopefully he will be a scholarship candidate. Thanks for all the opinions and information, it was immensly helpful.