Study	Reason for exclusion
Al‐Dabaan 2016	Ineligible research design (uncontrolled, repeated cross‐sectional design)
Cerezo 2004	Ineligible research design (interrupted time series)
Flemington 2017	Ineligible research design (uncontrolled, repeated cross‐sectional design)
Hawkins 2001a	Ineligible research design (3‐sample independent groups design)
Hawkins 2001b	Ineligible research design (3‐sample independent groups design)
Humphreys 2021	Ineligible research design (study compared 2 training programmes head‐to‐head)
König 2020	Ineligible intervention (training programme focused on institutional safeguarding rather than mandatory reporting)
Lee 2017	Ineligible outcomes (outcomes assessed were efficacy expectations and outcomes expectations for child abuse and neglect reporting)
Letourneau 2016	Ineligible research design (interrupted time series)
Levi 2021	No impact evaluation reported (paper described key features of the iLookOut training programme and its instructional innovations)
Menick 2005	Ineligible research design (uncontrolled, repeated cross‐sectional design)
Morris 1982	Ineligible research design (uncontrolled post‐test only or single administration, cross‐sectional design)
NCT03758794	Ineligible comparison (study compared 2 training approaches head‐to‐head: online and face‐to‐face)
Paek 2019	Ineligible research design (uncontrolled, repeated cross‐sectional design)
Rheingold 2012	Ineligible comparison (study compared 2 training approaches head‐to‐head: online and face‐to‐face)
Rheingold 2015	Ineligible comparison (study compared 2 training approaches head‐to‐head: online and face‐to‐face)
Socolar 1998	Ineligible intervention (training programme focused on documentation of child sexual abuse examinations rather than child protection training to improve reporting of child abuse and neglect)
Sullivan 1990	Ineligible research design (uncontrolled, repeated cross‐sectional design)
Volpe 1981	Ineligible research design (uncontrolled, repeated cross‐sectional design)
Yang 2020	Ineligible research design (single group, pre‐ and post‐test design)