This is the second article in a series of three in this special issue on establishing a boundary object to foster network health and development. The first article laid out the theoretical rationale for an Improvement Network Health and Development Framework. This article details the efforts to develop a set of practical measures tied to this framework and to examine the reliability and validity of this system of measures. It presents evidence on the psychometric and statistical properties of measures developed from the Improvement Network Health and Development Survey that was created for this purpose. Rasch Rating Scale Analyses were used to guide the creation of the measures and hierarchical linear model analyses were used to examine their reliability at the school and network levels. We found that these measures both distinguish reliably among networks at a fixed point in time and have the capacity to differentiate among them in their rates of development over time. The results presented here indicate that this system of measures can provide reliable formative feedback to those engaged in attempting to launch and develop improvement networks. Furthermore, these results provide the technical underpinnings for a web-based tool, described in the third article, that feeds this evidence quickly back to the participating improvement networks.