The main purpose of this thesis is to focus on the children, by investigating whether various organisation models, integrated, interactiv and mixed co-operation, for co-operation between teachers and recreation instructors showed differences in regard to the children's development, well-being, and ability to absorb knowledge. Did various co-operation models for school/day centre affect the children's school performance, peer and adult relationship, well-being, and general school and day centre experiences? Were there any differences related to the school and living areas? Were there any differences between children with day centre experience, and those who had none when it comes to school subjects, school performance, well-being, self-confidence, and relations with friends? The children's best and worst memories from their day centres are also studied.The theoretical frame of reference for this study is Bronfenbrenner's ecological theory of human development. A sample of 1229 children from grade three (age 9) from three different years and 282 children from grade six (age 12) are included in the study. The children in grade 6 were studied in grade three. The children answered questionnaires in grade 3 and 6 and the teachers assessed the children's well-being and levels of knowledge.Children are from nine different schools. The schools also represent areas with different socio-economic backgrounds, i.e. inner-city schools, suburban schools, and schools located in multicultural settings. The results showed as a whole no differences between the different co-operation models concerning school performance, wellbeing, social competence and relations to peers and adult. Children in the multicultural settings were more positive in their attitudes towards school than the children in the other areas but they performed less well in mathematics and Swedish language. The children in the inner-city had the highest scores. There were no differences between living areas in the children's attitudes towards the day centre.Children who had attended day centres were more often rated by their teachers as being more pleased with their performance than children who had not attended day centres. Moreover, more children, expressed as a percentage, who had participated in day centre activities were judged to be fearless and willing to answer questions than those children who had not participated in day centre activities. Many children mentioned relations with peers and staff as examples of their best memories from the school/day centre. Can any conclusions be made about which of the three co-operation models-integrated, interactive, or mixed - is the best? There was no simple pattern showing that any one form of co-operation would offer more advantages to the children than any other.