My DS9 is in 5th grade and goes to 6th grade math. This year he has moved to a new private elementary school with the private middle and high school right across the street, so he just walks there every day for math. That is one of the reasons he switched to that school this year. It has been working really well, although his schedule doesn't align very well. It's totally worth it, though, because he loves math and it all works out in the end.
Had he remained in the public school he would have been the first kid that anyone can recall to be in the situation of needing to go to the middle school from the elementary. Several options were discussed, but nothing was ever decided. One plan was for me to drive him to the middle school either at the beginning or the end of the day for his math class, although there were no guarantees there would be a nice schedule match-up, and it had been made very clear to me from the very beginning of the subject acceleration (after 1st grade; it was more of a warning, really) that there would be no bussing and that we would be entirely responsible for transportation. Another option that was floated was a flipped classroom situation, where he was given a math curriculum online (never got to the point of discussing which curriculum) and then he could ask his regular 5th grade teacher any questions he had about the 6th grade math, and I'm assuming that would have taken place during the class's regular math work time. I had also floated the idea of EPGY on his own.
I agree that you should find the placement that fits now and then deal with the logistics as the come up. The private school option wasn't even on my radar at the time of the acceleration, but we explored our options as necessary.
Too, you never really do know what your DS will need in a few years. Your DS may outpace his older peers and need even further acceleration down the line, like my DD12 did. Situations and options change all the time and are hard to predict, so all you can do is make the best decision you can for now. Just do you best, see how things go, and adjust if necessary.
