In an Irish context, the cognitive level prole of primary (pre-transfer) and second level (post-transfer) students was obtained. This prole showed that virtually no 6th class primary school pupils (age 12.3 years), and little less than 10 percent of 1st year second level students (age 12.8 years) in this study, were at levels capable of formal operational thought. This type of thought, formal operations, is believed to develop in children between the ages of 11 and 15 years and it is necessary for meaningful engagement and understanding of many scientic and mathematical concepts. In response to the low numbers of students capable of formal operational thought, and in an attempt to address the lack of pedagogical linkage across the primary- second level transition in Ireland, the Cognitive Acceleration through Science Edu- cation (CASE) programme was adapted for use in the nal year of primary school and in the rst year at second level. Students' cognitive development levels were measured using Science Reasoning Tasks (developed by the Concepts in Secondary Maths and Science team in the 1970's) before and after the respective interventions, and compared with non-intervention groups to assess the eectiveness of the pro- grammes. Statistically signicant cognitive gains were found for the intervention groups at primary level (0.51 (standard deviation)) and second level (0.52 ). When the Learning And Study Strategies Inventory (High School) was used to de- termine if there was a correlation between the 1st year students' motivation and the eect of the intervention programme on their cognitive development, no correlation was found. In an attempt to increase the sustainability of CASE in second level classrooms, a series of lessons, based on the CASE methodology, were developed in the context of six Junior Certicate science topics. These lessons were implemented in the second year and analysis of cognitive change showed a large eect size (1.74 ). There was also a signicant dierence between the performance of students in the intervention group, compared with the non-intervention group, on tests assessing conceptual understanding. Again no signicant correlation was found between the eects of the intervention on students' cognitive development and their motivation, implying that the CASE methodology contributed to the enhanced cognitive development. This work has shown an equal increase in cognitive development whether imple- mented in 6th class of primary school or in 1st year at second level. The eect size on students who were taught through both programmes was double that of those who completed only one programme. Implementation of the CASE methodology in 2nd year had an even greater eect on students' cognitive development.