In contemporary education policy, simplified technical accounts of policy problems and solutions are being produced with the use of numeric calculations. These calculations are seen as clear and unbiased, capable of revealing "what works" and identifying "best practices." In this piece, the authors use resources from the material-semiotic approach of actor-network theory to discuss how calculations have begun to serve as a subtle infrastructure underpinning the way we understand and organise our world. They demonstrate the usefulness of the approach in tracing the technicisation of policy by deploying it to qualitative studies of like-school comparisons in the two unexpectedly linked locations--New York City and Australia. The authors reveal how technical accounts are precarious and need constant maintenance to endure, even as they increasingly becoming routine, curtailing the policy imagination and limiting the spaces of contestation. It is for this reason, they argue, that a deeper understanding and sustained critique of such accounts is of pressing importance.