Footnotes

• Twitter @osmanhahmed, @VickiAn28323584, @BenjaminBrett1, @griz1, @DrKimHarmon, @drtinamaster, @jonpatricios, @Kat_Schneider7, @TamaraCVMcLeod, @SammoWalton

• Contributors GAD served as the primary author and responsible for all aspects of the project, including initial preparation, coordination, review, editing and final preparation of the Child SCAT6 tool. RJE served as the primary author of the systematic review and development of the SCAT6 manuscript and tool. All co-authors contributed to the development and critical review of the Child SCAT6 tool, and approved the final version of the tool.

• Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

• Competing interests GAD is a member of the Scientific Committee of the 6th International Consensus Conference on Concussion in Sport; an honorary member of the AFL Concussion Scientific Committee; Section Editor, Sport and Rehabilitation, NEUROSURGERY; and has attended meetings organised by sporting organisations including the NFL, NRL, IIHF, IOC and FIFA; however has not received any payment, research funding or other monies from these groups other than for travel costs. Dr RJE is a paid consultant for the NHL and cochair of the NHL/ NHLPA Concussion Subcommittee. He is also a paid consultant and chair of the Major League Soccer concussion committee and a consultant to the US Soccer Federation. He previously served as a neuropsychology consultant to Princeton University Athletic Medicine and EyeGuide. He is currently a co-PI for a grant funded by the NFL (NFL-Long) through Boston Children’s Hospital. He occasionally provides expert testimony in matters related to MTBI and sports concussion,and occasionally receives honoraria and travel support/reimbursement for professional meetings. Dr OHA is a Senior Physiotherapist at University Hospitals Dorset NHS Foundation Trust (England) and is Para Football Physiotherapy Lead/Para Football Classification Lead at the Football Association (England). He also works on a consultancy basis with the Football Association as the squad physiotherapist to the England Cerebral Palsy Football squad and teaches on the Football Association’s Advanced Trauma and Medical Management in Football course on a consultancy basis. He has a Visiting Senior Lecturer position at the University of Portsmouth, England (unpaid). He sits on several disability sport committees including Para Football Foundation as Medical Unit Co-Lead (unpaid), the International Federation of Cerebral Palsy Football as Medical and Sports Science Director (unpaid) and the International Blind Sports Association as Medical Committee member (unpaid). He has Associate Editor positionsat the British Journal of Sports Medicine (unpaid) and BMJ Open Sports Centers for Disease Control and Prevention; Department of Defense - USA Medical Research Acquisition Activity, National Collegiate Athletic Association; National Athletic Trainers’Association Foundation; National Football League/Under Armour/GE; Simbex; and ElmindA. He has consulted for US Soccer (paid), US Cycling (unpaid), University of Calgary SH Red Concussions external advisory board (unpaid), medico-legal litigation, and received speaker honorarium and travel reimbursements (including CISG) for talks given. He is co-author of “Biomechanics of Injury (3rd edition)” and has a patent pending on “Brain Metabolism Monitoring Through CCO Measurements Using All-Fiber-Integrated Super-Continuum Source”(US Application No. 17/164,490). He is on the and is/was on the editorial boards (all unpaid) for Journal of Athletic Training (2015 to present), Concussion (2014 to present), Athletic Training NIH NINDS (R01 NS110757 2019-2024); NINDS (U54 NS121688 2021-2026); UCLA Brain Injury Research Center, UCLA Steve Tisch Brain SPORTprogram, Easton Clinic for Brain Health Clinical Consultant (provide clinical care to athletes): NBA, NFL-Neurological Care Program, NHL/NHLPA, Los Angeles Lakers Advisory Board (Non compensated): Major League Soccer, National Basketball Association, US Soccer Federation. Advisory Board (Compensated): Highmark Interactive Medicolegal: One or two cases annually Speaker’s Bureau: None. Stock Shareholder: Highmark Interactive stock options (2018).Other Financial or Material Support: Book royalties – Blackwell/Wiley Publishing: Prioritized Neurological Differential Diagnosis Other: None. Dr KMG has received grant funding from NFL for the NFL LONG study. He also serves on the NCAA Scientific Advisory Board in an unpaid capacity. Dr Kim Harmon Research Development Director, Pac-12 Conference Member, Pac-12 Brain Trauma Task Force Member, NFL Head Neck and Spine Committee Deputy Editor, British Journal of Sports Medicine Head Football Physician, University of Washington. Dr Stanley A Herring Co-founder and senior advisor, The Sports Institute at UW Medicine (unpaid) Centers for Disease Control and Prevention and National Center for Injury Prevention and Control Board Pediatric Mild Traumatic Brain Injury Guideline Workgroup (unpaid) CISG (travel support) NCAA Concussion Safety Advisory Group (unpaid) Team Physician, Seattle Mariners Former Team Physician, Seattle Seahawks occasional payment for expert testimony travel support for professional meetings. Dr MM Sport and exercise medicine physician working in private consulting practice. Shareholder of Olympic Park Sports Medicine Centre in Melbourne. Ex-senior physician at the Hawthorn Football Club (AFL) Ex-Chief Executive Officer of the AFL Doctors Association. Research grants received from the Australian Football League, outside the submitted work.Travel support received from the Australian Football League, FIFA and the International Olympic Committee to attend and present at international conferences. Member of the Scientific Committee for the 6th International Consensus Conference on Concussion in Sport. Honorary member of the International Concussion in Sport Group. Honorary member of the Australian Rugby Union Concussion Advisory Group. Independent Concussion Consultant for World Rugby. Dr CLM reports no financial COI Volunteer positions: Concussion team physician, Shipley School Board of Trustees, American College of Sports Medicine Board of Directors, American Medical Society for Sports Medicine Board of Directors, Pediatric Research in Sports Medicine Executive Committee, Council on Sports Medicine and Fitness, American Academy of Pediatrics Advisory Board, Untold Foundation, Pink Concussions, Headway Foundation Editorial Board, Journal of Adolescent Health, Frontiers in Neuroergonomics, Exercise, Sport, and Movement. Dr MMC has received research funding to the Medical College of Wisconsin from the National Institutes of Health, Department of Veterans Affairs, Centers for Disease Control and Prevention, Department of Defense, National Collegiate Athletic Association, National Football League and Abbott Laboratories. He receives book royalties from Oxford University Press. He serves as clinical consultant to Milwaukee Bucks, Milwaukee Brewers and Green Bay Packers and is Co-Director of the NFL Neuropsychology Consultants without compensation. He serves as consultant for Neurotrauma Sciences, Inc. He receives travel support and speaker honorariums for professional activities. Dr TVML is a paid member of the NFL Head, Neck and Spine Committee and an unpaid member of the USA Swimming Concussion Task Force. WPM - I receive royalties from ABC-Clio publishing for the sale of the books, Kids, Sports and Concussion: A guide for coaches and parents and Concussions; from Springer International for the book Head and Neck Injuries in Young Athlete; and from Wolters Kluwer for working as an author for UpToDate. My research is funded, in part, by philanthropic support from the National Hockey League Alumni Association through the Corey C Griffin Pro-Am Tournament and a grant from a grant from the National Football League. Dr DN - CMO, Canadian Football League (CFL) Medical Director, Edmonton Oilers Hockey Club, National Hockey League Medial Director, Edmonton Elks Football Club, CFL Dr JSP: Editor BJSM (honorarium), Member of World Rugby Concussion Advisory Group (unpaid), Independent Concussion Consultant for World Rugby (fee per consultation), Medical consultant to South African Rugby (unpaid), Co-chair of the Scientific Committee, 6th International Conference on Concussion in Sport (unpaid), Board member of the Concussion in Sport Group (unpaid), Scientific Board member, EyeGuideTM (unpaid) Dr. LP CASEM Board Member, President-Elect 2022-2023NIH R34 Grant for EPICC Study (Eye Problems In Concussed Children), Site PI Speaker at various conferences. Dr MP declares the following: Consultant, CMO, Major League Soccer, Senior Advisor, NFL Head, Neck NCAA-CARE-DoD 2.0, ended 2020. Have received honoraria and reimbursement for travel for speaking and conferences attended. Have written chapters for UpToDate and received royalties for the Netter’s Sports Medicine textbook. Have provided work as an expert for cases involving concussion, team physician and other sports medicine topics. KJS has received grant funding from the Canadian Institutes of Health Research (CIHR), NFL Scientific Advisory Board, International Olympic Committee Medical and Scientific Research Fund, World Rugby, Mitacs Accelerate, University of Calgary, with funds paid to her institution and not to her personally. She is an Associate Editor of BJSM (unpaid), Independent consultant to World Rugby and has received travel and accommodation support for meetings where she has presented. She coordinated the writing of the systematic reviews that informed Amsterdam International Consensus on Concussion in Sport, for which she has received an educational grant to assist with the administrative costs associated with the writing of the reviews (with funds paid to her institution). She is a member of the AFL Concussion Scientific Committee (unpaid position), Brain Canada (unpaid positions) and Board member of the Concussion in Sport Group (CISG) (unpaid). She works as a physiotherapy consultant and treats athletes of all levels of sport from grass roots to professional. Dr SRW reports receipt of honorarium from the National Athletic Trainers’ Association (NATA) for presentation and travel to the 2022 World Congress of the World Federation of Athletic Training and Therapy (WFATT). Dr Walton serves as the Chair of Marketing and Promotions for the WFATT and as a member of the Outcomes working group for the International Initiative for Traumatic Brain Injury Research (InTBIR). Dr Walton reports work on research projects funded by the National Football League (NFL), National Collegiate Athletic Association (NCAA), Department of Defense (DoD) and Department of Veterans Affairs in the United States, and these entities do not oversee or provide input on his research or service efforts. Dr KOY: is Editor-in-Chief of the journal Neuropsychology and receive an editorial stipend from the American Psychological Association. I am an unpaid consulting editor for the journals Archives of Clinical Neuropsychology and Journal of Head Trauma Rehabilitation. I am an unpaid member of the Scientific Advisory Committee for Brain Injury Canada. I am the chair of the Canadian Concussion Network, which is funded by a grant from Canadian Institutes of Health Research (CIHR) to my institution; I am principal applicant on the grant but receive no income from it. I am a principal investigator on another grant from CIHR from which I derive no income. I am a co-investigator on research grants from CIHR, the US National Institutes ofHealth (NIH), Brain Canada Foundation, and National Football League Scientific Advisory Board; I derive income only from the grant from NIH. I serve as a member of a CIHR grant review panel for which I receive a small honorarium. I receive book royalties from Guilford Press and Cambridge University Press. I have received travel support and honorarium for presentations to multiple organisations. I served or serve on the following committees/boards for which I receive(d) honorarium: 1. Independent Data Monitoring Committee (IDMC), Care for Post-Concussive Symptoms Effeciveness (CARE4PCS-2) Trial, National Institute for Child Health and Human Development 2. Observational Study Monitoring Board (OSMB), Approaches and Decisions in Acute Pediatric TBI (ADAPT) Trial, National Institute of Neurological Disorders and Stroke National Research Advisory Council, National Pediatric Rehabilitation Resource Center, Center for Pediatric Rehabilitation: Growing Research, Education and Sharing Science (C-PROGRESS),Virginia Tech University. Dr RZ has current or past competitively-funded research grants from Canadian Institutes of Health Research (CIHR), National Institutes of Health (NIH), Health Canada, Ontario Neurotrauma Foundation (ONF), Ontario Ministry of Health, Physician Services Incorporated (PSI) Foundation, CHEO Foundation, University of Ottawa Brain and Mind Research Institute,Ontario Brain Institute (OBI), and Ontario SPOR Support Unit (OSSU) and the National FootballLeague (NFL) Scientific Advisory Board. I hold Clinical Research Chair in Pediatric Concussion from University of Ottawa, and I am on the advisory board for Parachute Canada (a non-profitinjury prevention charity) and the board of directors for the North American Brain Injury Society (unpaid). I am the co-founder, Scientific Director and a minority shareholder in 360 Concussion Care, an interdisciplinary concussion clinic.

• Provenance and peer review Not commissioned; internally peer reviewed.

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