This study focuses upon the effectiveness of structured co-operative group work on primary school students, aged between 8.5 and 9.5 years old, regarding their content knowledge, attitudes towards co-operative group work, experiential learning and open-ended curriculum as well as students' social and learning behaviour during co-operative group work. A cross-curricular educational programme was implemented within the curriculum area of environmental studies entitled "traffic education". The methodology applied in this study was the experimental and the case study research designs. The findings of the present study support the view that pupils can gain benefits through structured group work co-operation in obtaining content knowledge and group work skills, as well as in developing positive attitudes towards group work, experiential learning, open-ended curriculum and the co-operation with their peers with learning difficulties (LDs). Changes in the relationships with the peers were not affected after the implementation of the educational programme.