School-age children with behavioral and mental health disorders struggle every day in relationships with adults and/or peers at home, school, and during formal and informal activities. Pediatric primary care providers (P-PCPs) need to identify signs struggling children display, ant then assess and intercept the behaviors that adversely affect normal developmental patterns in social, emotional, and behavioral health. This chapter provides the best available evidence for the assessment, diagnosis, and treatment for school-age children with behavioral health problems and disorders. P-PCPs need to view behavioral and mental health with the same lens that physical health and well-being are viewed if the outcomes for children with behavioral health problems are to improve. The nutrition and gene mutation information must be considered in the diagnostic process to establish a full picture of the underlying cause of a child’s presenting problems.