This article describes how the Cognitive Acceleration through Science Education (CASE) programme was implemented in the final year of primary school and the first year of secondary school in a number of schools in Ireland. The original CASE programme, pioneered in the 1980s, proved successful in its aim to develop the science-reasoning abilities and achievement of 12- to 14-year-old pupils in the UK. The effectiveness of the programme, delivered in the primary-secondary school transition context, is reported in this article.