We held our son back a year in first grade due to developmental/maturity characteristics that were making it difficult for him to function in class. He had the cognitive ability of his peers, but the maturity of a younger child which was causing him other issues. It was a difficult decision to make, but ultimately the best one for him. He has a late birthday as it is, so he was one of the youngest and one of the least ready to move on with the rigor of higher grade levels at the time. Giving him that extra year gave him time to grow into himself. At that young age, it had little if any social impact (it would be different beyond about 2nd grade). He did well and is graduating in a few months. It was the right decision for him.