In the Irish education system, there is little continuity between the primary and secondary education systems. The transfer between these systems is particularly problematic in the area of science. In order to alleviate some of these problems, as well as to enhance the cognitive development of students, the Cognitive Acceleration through Science Education programme was adapted for use and implemented across the primary-secondary school transition in Ireland. The programme was delivered in a variety of ways across the two levels, including the teacher and researcher teaching the programmes individually and team-teaching arrangements. The results on cognitive development measures showed that the students who were taught the programme in primary and secondary school made significant gains, when compared to the non-intervention group. There were also gains evident for students who only received one part of the programme (i.e. in either primary or secondary school). The greater gains, in terms of effect size, were evident at secondary school. The rationale, methodology and results are detailed in this paper.