The aim of this study is to assess the effectiveness of the mindfulness Mindkinder-based programme on school adjustment, school behavioural problems and school outcomes in elementary education students. A quasi-experimental design of repeated pretest-posttest measures with control group is used. The participants in the study were 118 students (55.2% were girls and 44.8% were boys). The age of children ranged from 5 to 6 years (M = 5.69, SD = 0.37). The programme is implemented during school time. The results show that the program promoted in the experimental groups some significant improvement in school adjustment variables, school behavioural problems and school outcomes. These results suggest that mindfulness programmes can be effective in promoting school adjustment and improving school outcomes in childhood. The implications of these findings are discussed and recommendations are formulated for future research.