This article provides evidence that schools can influence parents' involvement in education, and this has causal effects on pupils' behaviour. Furthermore, it shows how the impact of more involved parents on their children is amplified at the class level by peer group interaction. We build on a large-scale controlled experiment run in a French deprived educational district, where parents of middle-school children were invited to participate in a simple program of parent-school meetings on how to get better involved in their children's education. At the end of the school year, we find that treated families have increased their school-and home-based involvement activities. In turn, pupils of treatment classes have developed more positive behaviour and attitudes in school, notably in terms of truancy and disciplinary sanctions (with effects-size around 15% of a standard deviation). However, test scores did not improve under the intervention. Our results suggest that parents are an input for schooling policies and it is possible to influence important aspects of the schooling process at low cost.