This paper assesses the cumulative long-term impact of successive years of high quality provision in schools. This was achieved by looking at the consequences, up to the age of 11 (Year 6), of attending a school where there was high or low value-added in each of the 7 years of primary education in England. Multi-level models for thousands of pupils were set up in which the relative contribution of the school was estimated each year, as was the impact of attainment levels reached in each previous year. The analyses indicated that: relative progress each year was important but progress in the earliest years was the most important. Good progress in the first year at school was still detectable in the last year of primary schooling. Boosts or setbacks to progress in one year can be added or subtracted to progress in another. The relative importance of school for maths and reading were similar but smaller for vocabulary. The analyses suggest that teachers are of key importance when considering educational effectiveness and the implication for policy makers and school effectiveness researchers are discussed.