We are in the process of redshirting our eldest. He turned 5 in May and technically could have started Kindergarten, but we're keeping him out until next year. A few things went into that decision. First, he has a few health issues that, while not serious, have left him small for his age and emotionally immature. Second, he would have been among the younger kids in his grade. Third, when we spoke to his future principal, she said that her preference would be that all boys start Kindergarten after they turn 6. She said most boys just aren't ready emotionally and spend the entire year being told "no" and "sit down" and "be quiet" until they start hating school. She said the 6 year-old boys do much better and seem happier.
That said, I'm really struggling with this decision after-the-fact. My son is smart and social and very interested in going to school. He's sad that the other kids his age are in school when he's not (no playmates at the park!). He gets a little melancholy when the school bus goes by in the morning. I'm also worried that he'll be too advanced for Kindergarten because he LOVES to do "school work" with me. We're trying to slow him down by doing piano lessons, art classes, gymnastics, and other activities during the day, although it's not really working to slow him down. But mostly, I'm relying on the fact that - if he finds Kindergarten too easy - we can always skip him up to First Grade (or skip First Grade and go to Second at the beginning of the next school year).