Esther Mertens

50 | Chapter 3 whereas the Light and Plus conditions consisted mostly of students with a Western background. Therefore we controlled for age and ethnic background in all analyses. Attrition. Little’s MCAR test indicated that the data were not missing completely at random (χ 2 (2339) = 2539.54, p = .002). Attrition analyses were conducted for the demographic and outcome variables between students who dropped out ( n T2 = 68, n T3 = 83, n T4 = 60) and who remained in the study. Concerning the demographic variables, there were no differences on age ( F (1,1230) = .24, p = .626, η 2 partial = .000), sex distribution (χ 2 (1) = .1.36, p = .244, φ = -.033), and ethnic background (χ 2 (1) = 1.19, p = .276, φ = .032). Concerning the outcome variables, three MANOVAs, one per time point, showed that there were differences on the outcome variables at T1 ( F (39, 3591) = 1.45, p = .035, η 2 partial = .016), but not at T2 ( F (39, 3363) = .72, p = .898, η 2 partial = .008) and T3 ( F (26, 2032) = .74, p = .824, η 2 partial = .009). When further examining the differences between students who dropped out and who remained in the study after T1, the univariate test indicated that drop-outs differed from completers on externalizing behavior ( F (3, 1207) = 3.00, p = .030). However, this difference was not significant anymore after Bonferroni correction ( p = .124). As Little’s MCAR test yield conservative results when applied to a large set of variables and because we found no differences between drop-outs and completers on the demographic or any of the outcome variables, we regarded the missing data as missing at random (Van Ness, Murphy, Araujo, Pisani, & Allore, 2007). Conditions R&W. R&W uses a psychophysical approach, integrating play and exercises to learn students how to make (physical) contact with others, and explore, respect, and set own and other’s boundaries. The exercises are developed to enhance competencies as well as to prevent problems in students’ intra- and interpersonal domains. For instance, according to the theory of R&W, students practice walking with an upright posture and experience that this has an influence on how they feel; if they walk with their head high, they feel more confident. In other exercises, students focus on their muscle tension and breathing which is theorized to raise their emotional awareness. They practice relaxing their muscles and lowering their breathing to regulate their emotions and become calm, less stressed and less aggressive. Students also engage in role-plays to practice, for instance, how to set and indicate boundaries, how to react calmly to provocations, and how to help students who get bullied. During the intervention, the symbolic principles of ‘rock’ and ‘water’ are used to indicate opposite ends of a spectrum: An uncompromising attitude in which the student is able to resist pressure from others (i.e., rock) to a flexible attitude in which the student is open to the opinions, thoughts, and feelings of others (i.e., water). The intervention is a 2-year manualized program. In the first year, students received 14 R&W lessons and in the second year 8 R&W lessons. The lessons were implemented