My DS was one of the youngest. I copped a lot of flack. But I'm glad he went. He is probably now one of the more mature boys, has no problems socialising and is not suffering academically. He is also the second child. So I think every child is different. However I think the cost of keeping a child back, or the inconvenience of doing so should never ever be a reason to send a child to school. School readiness is so important. And the individual needs of each child.