In this paper, a site ontological approach to practice seeks to understand how educational development can be accomplished through the practices of 'middle leaders'--educators who exercise their leading 'between' the principal and the teaching staff. Analysis of two vignettes of leading in extraordinary circumstances untangles the web of interrelationships, conditions and practices that comprise middle leading in schools. The discussion focuses on how middle leaders' practices are enabled and constrained by practice architectures, and how their leading is ecologically arranged with other educational practices present. It is argued that notions of 'best practice' are an idealised but erroneous myth that often provokes educational development to be practised in homogenised or pre-packaged ways that do not necessarily serve the needs and interests of schools. We conclude by suggesting that best practice might be better conceptualised as site based practices, uniquely realised in response to local issues and concerns.