They argue that other European children start later and learn more efficiently. Chief inspector Chris Woodhead suggests teaching standards might have more to do with it.
Officially, the starting age here is the term after a child's fifth birthday, but most enter school in the year they are five: numbers of four-year-olds in reception classes have risen 40 per cent in the past decade to 355,000.Many September starters are still three now.
Why? Parents feel pressured to get their children into school because of childcare problems, and because schools warn that a place might not be available later. Tiny bums on seats equal cash for schools. A results-hungry government is not going to argue.
The new early-years curriculum, which treats reception as the end rather than the beginning of a stage, should help. But a joined-up effort to provide a real choice of education and care to suit the individual needs of under-fives - and better still, under-sixes - is desperately overdue.