Objectives: To evaluate, under randomized field trial conditions, the deterrent effects of a police–school partnership, called the Ability School Engagement Program (ASEP). The partnership sought to co-produce truancy reduction by actively engaging parents and their truanting children in a group conference dialogue that was designed to increase parental and child awareness of the truancy laws (and the consequences of noncompliance), and thereby foster students’ willingness to attend school. Methods: Using a randomized field trial design, 102 truanting young people were randomly allocated to a control, business-as-usual condition (n = 51), or the ASEP experimental condition (n = 51). In this paper, we use mixed model ANOVA and multiple regression analysis of self-report survey data from both students and their parents to assess differences between the experimental and control group on parental perceptions of prosecution likelihood and student willingness to attend school. We use qualitative analysis of the group conference transcripts to examine how the intervention affected these factors. Results: Our results demonstrate that the police–school partnership intervention increased parental awareness of prosecution likelihood, which moderated students’ self-reported willingness to attend school. Conclusions: We conclude that police–school partnerships that engage parents and their children to better understand the laws pertaining to school attendance are a promising approach for co-producing the reduction of truancy.