I don't see that its a problem having 4.5 as an option if a child is ready for it but if it means that other children who mightn't be ready have to start earlier then I would think it a bad idea. In Raising Boys Steve Budulph says that he thinks that the starting age for boys should be a year older than girls because thier communications skills develop more slowly so maybe the starting age should be set at between 4.5 and 6 years and rather than looking at ages we should be looking at skills.