In response to the urgent need for teachers to be better equipped with strategies for responding to students who suffer the effects of complex trauma (CT), this inter-disciplinary study investigated the lived experiences of professionals (social workers, psychologists, criminal justice workers and community workers) working with school students with CT in out-of-school contexts. The aim of this study was to formulate strategic approaches from the expertise of out-of-school professionals and specialists that might be adapted for use within pre-service teacher education programs to better prepare the next generation of teachers with the skills needed for working with trauma-affected students. Using a phenomenological methodology and working through an ecological-psychosocial theoretical lens, this qualitative study found three key categories of understandings and skills used as a common approach amongst specialists working with students suffering the effects of CT: an applied understanding of child development, a capacity to read and adjust classroom environment and climate; and underpinning theoretical knowledge of the effects of trauma on young people's behaviour.