Language difficulties persist in a proportion of young people first identified in their early school years (Bishop and Adams, 1990; Stothard et al., 1998), and speech and language therapy (SLT) within secondary education is a developing area of expertise. This article briefly describes the rationale for collaboration between teachers and SLT within mainstream classes to support students aged 11 years and over with language learning difficulties. One aspect of the collaborative practice--namely, vocabulary teaching using robust vocabulary instruction (Beck et al., 2002, 2008)--is described, together with a preliminary attempt, using concept maps (Novak, 1998), to gauge the impact of this collaboration on teacher understanding and thinking about vocabulary teaching. Using concept maps pre- and post-collaboration with three teachers it was possible to identify positive changes in teacher knowledge and understanding, which may have occurred as a result of the collaborative practice. (Contains 8 figures.)