From the Acceleration Institute (Belin-Blank) website:
http://accelerationinstitute.org/Resources/QA/"The years just before a move to another building, especially between elementary school and junior high or middle school, are difficult times for acceleration. These are considered “transition years.” For example, if the school district’s elementary schools end at 4th grade, and middle school is for 5th-8th graders, the common sense approach would suggest having the potential accelerant skip 4th grade and go straight into 5th grade. This seems sensible because then the accelerated student is one of many new students in a new school, and it is less likely that he or she will “stand out” in the class. While common sense dictates that it is best for a student to skip grades before moving into a new building, clinical data from the Belin-Blank Center indicate otherwise. A move to the next level generally involves a change in the way the school day schedule and extracurricular activities are organized. School personnel often use trips to the new building and other processes to prepare students for the upcoming move. Today, schools don’t just have one spring “move-up day” in which students can go to visit their new buildings. Instead, homework expectations and student responsibilities are introduced and taught throughout the transition year so that, by the end of the transition year, the students know what to expect during the next grade level. It may be better to accelerate during the year previous to the transition year so that the student can participate fully in these transition year activities.
Sometimes, though, circumstances require that acceleration take place during a transition year. The involvement of current and receiving teachers and the administration at both schools is critical in cases where grade skipping involves a building change. In such instances, it is important to provide students with experiences that allow a preview of classes in the new setting."
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It's a bit more nuanced than "yes" or "no" on skipping a transition year. Consider that early admission, even to first grade, is generally viewed positively, and that's a transition-year skip. Personally, both I and my children have skipped entering and departing transition years, as well as accelerating within the same building. There are going to be pros and cons no matter what. That's why the IAS (and acceleration/retention decisions in general) use information from multiple sources and types.
And please don't take on responsibility or guilt for the challenges faced by the young person in your DC's class who may or may not have been an appropriate candidate for the placement! We don't know the full story (nor do we need to); there may be other factors outside of the placement itself that are affecting their current struggles. These decisions are complex, and without guarantees.
