Educators usually recognise the value of drama-in-education, but hesitate to use it with unpredictable diverse groups that have limited communication and social understanding. This article evaluates a professional development initiative in an all-age special school (3-19 years) in eastern England as a whole-school improvement strategy to promote drama for enhancing children's communication through dialogic teaching. The project was the culmination of an action research cycle to refine an original constructivist five-staged professional developmental model for teaching inclusive groups with children with special educational needs and disabilities. Following a staff training session, the researcher supported each teacher in class once a week for 6 weeks, using collegial mentoring strategies. The model enabled their starting point and priority next step to be accurately identified towards them gradually taking over leading drama sessions. A pedagogical framework for early drama -- Prescribed Drama Structures -- proved pivotal, enhanced by a flexible model for exploring story and understanding social narrative.