Such reforms will give every child the best start in life and so extend the ladder of opportunity into even the poorest households. Or at least, that is the theory. At first glance yesterday's study from Durham University casts doubt on whether it translates into practice. Across a huge sample of 35,000 children starting school since the millennium, the researchers find no improvement in cognitive abilities, and - just as importantly - no narrowing in the performance gap between deprived children and the rest. Does it follow that the £21bn that ministers boast that they have spent on pre-schooling is taxpayer money down the drain?
Emphatically not. For one thing, on closer reading the Durham results look a little less shocking. Even the youngest school-starters examined were born around 2001, a time when Sure Start itself was in its infancy, so few of them have experienced the programme's full effect. Nor did the analysts have information about what type of childcare or pre-schooling pupils had undergone. Previous studies, however, have shown quality is crucial. More definitive judgment on whether Sure Start works awaits a Birkbeck study at the end of the year, based on data that is tailor-made for the job. Even then, more nebulous goals - such as relationship building - will remain hard to measure, yet American experience suggests that it is through such means that pre-school services do most to protect the poorest children from drifting towards a life of crime or worklessness.
So ministers have solid reasons to hold their nerve. But when all the international evidence suggested expanded pre-school would boost attainment, it is disappointing that this is not yet starting to happen. One problem may be that the sheer pace of expansion is adversely affecting standards - a risk that Ofsted identifies today as it releases figures showing that the proportion of high-quality childminders is down. Supporting children through their early years is the most pressing of social priorities. Ministers must now ensure that quantity is not achieved at the expense of quality.