It would be a good idea to talk to your child's teacher at preschool. They would be able give you a good insight.

I am a primary school teacher and I have taught kindergarten for over 15 years. (gee I sound so old!) in my experience, most parents are now holding their children back until they have turned five. I have 2 boys and I am lucky that they will both be 5 before they start school. Your child may exhibit signs that they are ready academically but it is the social aspect that may be a concern, especially if there are children in the room who have already turned 6- that would be a 1 1/2 year age gap! I have recommended to many parents and friends to hold their children back for that extra year. My personal experience has shown me that It will benefit them in the long run.