Red-Shirting Kids For Kindergarten – To Hold Back Or Not To Hold Back

I heard about this fascinating topic on the radio and scrambled to find out more. Since I've enrolled my own kids in school, I've noticed parents being concerned about their kids' ages as they got ready for kindergarten. Would they be ready when school started? Would they be one of the smallest kids in their class? Perhaps another question is this - how much does their kindergarten age really matter?