Originally Posted By: Mr and Mrs P
I think that a year of partial middle school will help develop the EF skills he will need going forward.
In general, a year of IEP/504 remediation/accommodation to scaffold and direct-teach EF skills may help develop these missing/emerging skills, whereas a year without these explicit supports may not help him gain these skills simply by casual observation of what others do. Here is one old post about grouping accommodations and here is a post listing several resources on EF skills.

We will soon be having a meeting with the committee to decide whether to accelerate DS fully into fifth grade at the end of third.
Will the committee be utilizing the Iowa Acceleration Scale (IAS)?

How is he doing socially? Does he have school friends in his current grade level? Does he know kids in the next grade level from extracurriculars such as music, sports, summer camps? Does he make friends easily and readily adapt to new situations? Is he athletic? How does he feel about acceleration, and the options available?

From your post, it looks like options offered include:
- Full grade acceleration to fifth grade
- Fifth grade reading curriculum in his fourth grade classroom.

It is possible that other options could be considered, such as:
Fourth grade, with IEP/504 to remediate/accommodate EF issues, including an aide to walk him to/from 5th grade math at the middle school building. Fifth grade reading curriculum could be in his fourth grade classroom OR aide walks him to/from 5th grade reading at the middle school building. This could provide him with fourth grade gym class which may be a benefit if he is not particularly large and/or athletic. A combined year of 4th grade classes and 5th grade classes could also help him develop friendships with the next class while retaining the ability to see current friends on a daily basis at school.

Edited to add a link to this current thread on a somewhat related situation: skipping grade vs. subject acceleration for gifted.