If I had a dollar (or rather a euro - believe it or not, this issue is universal) for every parent who told me they�d never accelerate their child) and a bonus 50c for every one who told me how great it was for their child to be held back...sigh.
It appears to be almost a knee jerk reaction, to make sure you�re feeling a bit worse for thinking your child is smarter than theirs.

Guess what - your child probably is. And that�s why being held back would have been a disaster, and grade level a slough.

I�ve become very jaded, with one child one year ahead (entered early, refused second skip), one child almost two years ahead (young for grade and subsequently skipped), one child old for grade (just a couple days after the cutoff, so really a year behind, at least for our family lol). Each time unique circumstances for a unique child, unique decisions and loads of sceptics and second guessers on the way putting in their 2 cents.

Are their concerns, your concerns, valid? Yes, skipping is rarely the ideal solution, and there may be bumps in the road. It is, however, usually a much better solution than leaving a HG+ kid in the age grade.

If someone insists that differentiation works just fine for their kid, either their teacher is a superstar (I am assuming they exist) or, more probably, the difference between their kid and the average kid in class is not that great - either the kid is not that smart, or the other kids aren�t exactly that average, depending on the demographic of the school.