My son was homeschooled for grades K-4. We put him in school this past fall. He is 5th grade age but we put him in 6th grade in school. He was ready for algebra, but we decided to aim low and started him out in prealgebra (7th grade math) but it became rapidly apparent that he needed to move into Algebra I. So he is accelerated 3 years in math and 1 year for everything else right now. We have decided (with the school's enthusiastic blessing) to have him skip 7th, so he will be entering 8th in the fall.
The transition has been fairly smooth. The school is very supportive of his acceleration, which is immensely helpful. It is a small school (only 6 students in the 6th grade, for example) so the culture is quite different from what you find in larger schools. The kids aren't hung up on grade level at all. So I guess what I'm trying to say is that the school culture is very important for a smooth transition.
I think it has helped to do the acceleration in stages. The initial skip into 6th with 7th grade math and then a few months later the skip into Algebra I. By that time it was obvious to everyone involved that that skip was necessary. And now after a year in 6th grade it is apparent that the skip to 8th is needed as well. I think if we had just plopped him into 7th grade and Algebra I at the beginning of the year things might have been rockier and any problems might have been blamed erroneously on the skip.
The thing that has been more difficult has been the increased output expectations. This is mainly a problem in the algebra class. Related issues are things like organization, writing neatly, time management, and so forth. I have been giving him a lot of support with the executive functioning stuff, with the idea being that he will gradually take over in a year or two.
