DS5 just turned 5 this week and is starting K next week. So definitely NO holding back, more like "skipped by nature" as I call it since he was born early and only thanks to that doesn't have to wait another year to go to school. His fine motor skills are lacking but other than that, he's more than ready to go. He is not very sporty so he wouldn't be joining the teams no matter how long we'd wait. Academically we have no concerns. He will probably be one of the smallest kids in his class and probably the youngest one as well but we're not concerned. At least not at the moment.