Objective: This study examined parents' participation in a school-and home-based prevention and early intervention service model designed to promote positive parenting and parent involvement in schooling. Method: Paraprofessionals (n = 32) employed by four social service agencies provided parenting support and education through parent groups, home/community visits, case management, and individual contacts to African American and Latino/a families in urban high-poverty communities (n = 375). In this open trial, we identified longitudinal trajectories of parents' participation across all service formats over the course of a full school year using latent class growth models, then examined group differences in baseline child and family characteristics, participation in specific service formats, and parenting skills practice across the year. Results: Four distinct trajectories were identified: parents with consistently low participation; parents whose participation declined and subsequently rebounded; parents with increasing participation; and parents with consistently high participation. Significant differences between trajectory groups were identified on baseline child and family characteristics, and the number and types of service formats in which parents participated participation. Parents across trajectories consistently practiced parenting skills over the school year, with parents who demonstrated increasing participation over time showing the most growth in the number of skills practiced each month. Conclusions: Unique patterns of parent participation across a school year in paraprofessional-delivered services indicates the promise of capitalizing on multiple opportunities to engage parents and suggests the potential for paraprofessional staff to overcome longstanding disparities in parent involvement in children's mental health services.