If you are going to grade-skip your DS, I would really push to move him into 5th grade at the beginning of 3rd quarter so that he can be up to speed with the 5th graders' writing and executive function expectation ASAP. In our area, 5th to 6th grade is a significant leap forward because our middle school starts in 6th. It's a big adjustment for all the kids but it will be easier if your DS has been treated as a 5th grader during the second half of the year. In the second half of 5th grade last year, DS/DD's teachers tried to introduce some middle school expectations and otherwise prepared them for middle school. While he will need to answer promptly as class discussions move quickly, that is something that he can work on now so that he can be comfortable by 6th grade.