Intervention and evaluation design

The evaluation of this school-based, teacher-centered intervention (“Join the Healthy Boat”) is a prospective, stratified, cluster-randomized, and longitudinal study including an intervention group (IG) and a control group (CG). The study participants were recruited in several ways. For example, information about the study was disseminated by education and health authorities, university schools of education, electronic newsletter, television and radio, and adverts in training catalogs for primary school teachers throughout Baden-Wuerttemberg (South-West Germany).

After the recruiting period, 94 schools were assessed for eligibility. Before randomization three schools declined to participate for unknown reasons; subsequently, 91 primary schools were randomized, 45 schools were allocated to the IG and 46 schools to the CG. One school in the IG withdrew from the participation because of the commitment required for participation was found to be too much, and four schools in the CG because of the randomization in the CG.

At baseline, data of 1,943 first and second grade primary-school children in 157 classes (81 classes in the IG; 76 classes in the CG) were compiled. During the intervention year, one school of the IG withdrew their participation because of unknown reasons and two schools of the CG withdrew due to parental request, while the other school was destroyed by fire. Further information about the recruiting process has been published in Dreyhaupt et al. 2012.

At the beginning of the school year 2010/2011, after baseline measurements were taken, the intervention started in the IG. Simultaneously, the CG followed the regular school curriculum without the intervention. Follow-up measurements (T2) were taken after one intervention year, in the school year 2011/2012. After the T2 measurement, the CG started with the intervention too. Further details about the evaluation design, the program and other aspects of the evaluation study have already been published elsewhere (Kobel et al. 2014; Dreyhaupt et al. 2012). The study was approved by the Ministry of Culture and Education and the university’s ethics committee and is in accordance with the Declaration of Helsinki. The study is registered at the German Clinical Trials Register (DRKS00000494).