The majority of mental health problems begin in childhood or adolescence. The potential benefits of early identification and treatment of such problems are well established, and models of effective mental health interventions for children have proliferated in recent decades. However, barriers in access to care and challenges in assuring delivery of high‐quality care significantly limit the public health impact of services for children and families. Specifically, the majority of children who need mental health care do not receive it, and when children are in care, many do not receive interventions that are most likely to have the greatest positive impact. A commitment to social justice requires significant improvement in access to care and quality of care to maximize human potential. The purpose of this manuscript is to highlight promising scientific advances in the development of effective mental health services for children and families, as well as the vexing challenges of actually delivering these services to those most in need. Key challenges to be discussed include disparities in access to care and quality of care, including race/ethnic disparities and complexities of navigating the multi‐sector mental health service system for children, and difficulties in implementing effective intervention models more consistently in community care. The authors will propose practice and policy reform recommendations to address these challenges. Copyright © 2017 John Wiley & Sons, Ltd.