The purpose of the present study was to analyse possible developmental trends in sustained attention through the pre-school period, as well as the influence of social and physical distractions. Three samples of children, one per each pre-school grade, were observed during learning activities required by the teacher. Children's behaviour was coded as sustained attention, and as social and non-social categories of disengagement. Sustained attention was observed to linearly increase with pre-school level, while the frequency of social interference of attention decreased. These findings are discussed within the context of studies on developmental trends of sustained attention in natural settings, the influence of social stimuli and the possible involvement of self-control abilities.