The evidence for and against an early start is not at all clear-cut. This became clear in a review of the literature on the numbers of terms at school that I carried out for the School Curriculum and Assessment Authority recently.
Probably the strongest evidence in favour of an early start comes from our own work within the project at Durham. It has shown the very great strides made by pupils of all ages during the reception year. Further, we have just reported evidence for the positive impact of effective reception classes on the progress made by pupils two years later. But we are not complacent. This is a complicated area and the jury is still out. Research has a long way to go before it can make definitive statements in this area - if it ever will.