Sorry for such a late reply, I'm just seeing the thread now.
I have 8 yr old identical twins, both tested HG. Their scores and profiles from testing are remarkably similar. They are best of friends, but have some difference in their choice of other friends. They are competitive with each other, but unfortunately not in a good way. One continually tries to do better than the other, who then reacts by backing off and pretending disinterest. On the other hand, they always have someone to talk about their passions with, and who understands them completely.
They were in the same kindergarten class. There was only one class of their program, so no issues there. They did very well. I liked hearing them talk about their class when they thought I wasn't listening.
In first grade they had new city, new school, new baby sister and a Dad who was deploying. They did well together in K, so I asked them to be in the same class. This went well for a few months but then the teacher and I both wished they had been separated. They spent all their free time being clowns and distracting the other students.
They were separated in second grade and it was really nice to see them bloom separately. The only down-side was that there is only one other boy who shares their intellectual interests, and therefor only one of my sons had a peer in class. The boys still play together most recess and lunch periods. The program only had 2 classes, so they also saw each other every day when the two classes were combined for gym and music. They spent their free time reading or sometimes doing projects independantly.
This year, grade 3, the maximum class size went up, and there is once again only one class of their program, so they are together again.
A PP mentioned the issue of parent-teacher conferences. It isn't just the teacher that tends to flip back and forth between children, rather than focusing on one at a time. I am guilty too. When they are separated the teacher is never unsure of which child said or did something and neither of us are as tempted to generalize. When they are together it is easy to group them together. Both family and teachers have encountered situations when we are unsure of which of them said or did something.
Another person mentioned the issue of ease of differentiation within the classroom. It has also occurred to me that the more children, even siblings, in a class at the same level, the easier it should be for a teacher to differentiate. It makes sense to me, although it certainly isn't the only factor to consider. My experience so far has been that the teachers think it is a less important factor than I think it is, but we all agree that so far it has been moot, so I haven't explored the issue further.
While it is certainly easier for me to have them in the same class, and they like it, I do wish that they had another year apart to help gain some confidence on their own. IMO, the importance of this depends somewhat on the family lifestyle (whether there are activities they do separately at home, etc.) and on personality. They need to be confident on their own, but separate classes are not the only means to achieve this.
