Background: Formalised networks have become integral features of many education systems. Some networks have emerged organically as practitioners have sought to share and improve practice while others have been systematically planned and supported by policy makers in an attempt to raise the overall effectiveness of entire systems. However, despite their rising popularity the literature pertaining to their purposes, design and function remains limited. Furthermore, their impact on schools, teachers and students is even less clear. Purpose and sources of evidence: This article draws on the literature and the authors' research on school-based networks to explore their nature and contribution to school improvement. Main argument and conclusions: In conclusion, it is argued three specific areas warrant further investigation. First, the "constitution" or mix and balance of those involved in the network, second, the "relationships" or the interactions between those involved in the network, and third, the "purpose and identity" or the aims and objectives of the network and the identity those involved create for the network, and that a deeper understanding of these areas will go some way to realise the potential of school-based networks.