This mixed methods study was conducted in an urban school district with 172 schools. In schools, students who require mental health support are treated by school psychologists, school social workers, and school counselors. This study examines these clinicians' differing training, knowledge of, and clinical practice related to trauma, to determine if there are comparable levels of expertise across all three clinician groups and to identify knowledge gaps and/or training needs for universities and district-sponsored training and professional development. A quantitative word association task was administered to examine clinicians' perceptions of trauma. A qualitative, descriptive, focus group examined participating clinicians' trauma training, clinical experience, knowledge gaps, and anticipated training needs. For the word association task, results indicate some variability in clinician perceptions of abstractness and positivity-negativity in their perceptions of stimulus-response dyads based on trauma-related words. Across groups, females and social workers overall demonstrated significantly more positive and abstract impressions of word association dyad relationships reflecting trauma informed care, trauma responsive care, and trauma resilience. School psychologists were overall less positive. Focus group results indicate that trauma-related training to-date has been of benefit to the clinicians, but more training is needed. Practicing clinicians expressed that their university training and training being provided currently at universities is not sufficient, related to trauma. Strategies for training and to embed trauma informed practice into clinical best practice and culture and climate in schools are discussed, as well as implications for further research. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]