Gaps in education attainment between high and low achieving children in the primary school years are frequently evidenced in educational reports. Linked to social disadvantage, these gaps have detrimental long-term effects on learning. There is a need to close the gap in attainment by addressing barriers to learning and offering alternative contexts for education. There is increasing evidence for beneficial impacts of education delivered outdoors, yet most programmes are un-structured, and evidence is anecdotal and lacks experimental rigour. In addition, there is a wealth of social-emotional outcomes reported yet little in the way of educational attainment outcomes. The current study explores the educational impact of a structured curriculum-based outdoor learning programme for primary school children: "Wilderness Schooling". A matched-groups design: Wilderness Schooling (n = 223) and conventional schooling (n = 217), was used to compare attainment data in English reading, English writing and maths, collected at three time-points: Pre- (T1) and post-intervention (T2) and at a 6-week follow up (T3). Data show that children in the Wilderness Schooling group significantly improved their attainment in all three subjects compared to controls. Trajectories of impact indicated attainment continued to increase from baseline in the following weeks after the intervention concluded. These results allow the case to be made for the core curriculum to be conducted outdoors to improve children's learning. However, it is important to consider that there are likely to be various components of the intervention that could form a theory of change essential to reported outcomes.