Background: School professionals, including classroom teachers, school administrators, psychologists, teachers' aides, and nurses, often interact with students with concussions. To ensure they have the knowledge to identify and manage concussions, the U.S. Centers of Disease Control and Prevention developed the HEADS UP to Schools online training. Methods: The HEADS UP to Schools training includes a pre-test and post-test consisting of 16 knowledge questions in three areas (symptom recognition, school support and accommodation, and guidance and recommendations for school staff) and five self-efficacy questions. Pre- and post-test responses of 8750 individuals were compared and analyzed to evaluate the effectiveness of the training. Results: Respondent scores significantly improved between pre- and post-test responses for all knowledge questions and self-efficacy questions. Implications for School Health Policy, Practice, and Equity: Schools and school districts may consider offering this training to staff to help ensure that at least one person at each school is trained on concussion and to increase awareness of evidence-based practices. Conclusions: Knowledge and self-efficacy on concussion identification and management improved among school professionals who completed the HEADS UP to Schools training. Future research to assess whether concussion knowledge and self-efficacy are maintained long term may be beneficial.