The rapid expansion of public-school preschool programs significantly challenges America's school administrators, teachers, and school professionals. The complex issues of preschool mental health needs, expulsion, and suspension are at the forefront. In the United States, schools are reporting rapidly increasing numbers of preschool programs, primarily in the form of 3K, 4K, and inclusion programs. This dramatic increase of young children in the public schools is a result of (a) research on the long-term cognitive and social benefits of high-quality early childhood programs, (b) federal and state legislation supporting state-funded preschool education, and (c) the continued need to support working parents via public-funded education for their young children. This article is a review of the research on preschool mental health and early trauma from adverse childhood experiences (ACEs), the impact of suspension and expulsion on preschool children, and the benefits of high-quality preschool programs in the public schools. Also included is a review of current policies and practices in exemplary public-school preschool programs related to mental health services, ACEs, suspension, and expulsion. Recommendations for future policy and practices for the preschool population are presented. Appendix B provides resources for school administrators and professionals.