This fourth Innocenti Report Card seeks to measure and compare educational under-achievement across the industrialized world. Using data from two different surveys of students in 24 OECD countries, it presents the 'big picture' of how well each country's educational system is performing when measured by a) what proportion of students fall below given benchmarks of educational achievement and b) how far behind the national average the lowest-achieving pupils are being allowed to fall. It is clear that educational disadvantage is born not at school but in the home. And government efforts to contain that disadvantage - in order to foster social cohesion and maximise investments in education - must also take into account what is now known about early childhood development. The essence of that knowledge is not complicated: learning begins at birth, and a loving, secure, stimulating environment, with time devoted to play, reading, talking and listening to infants and young children, lays down the foundations for cognitive and social skills. No government can therefore ignore the issue of what happens in the preschool years.