We use two different data sets and three different instruments to estimate the impact of a long-established pre-school nursery programme on children's nutritional status. We use variables related to cost (fee, distance to the nursery) and programme availability (capacity of the programme in the town) as instruments. One of our data sets is representative of very poor individuals living in rural areas of Colombia, while the other focuses in urban areas and includes individuals relatively less poor. We find that programme participation increases children's height, with the size of the effect being consistent across the three instruments and the two data sets.