We describe our efforts to build a magnetic field sensor to be deployed in schools across the United Kingdom, adding to the existing variometer network from AuroraWatch set up by the University of Lancaster (Figure 1). The aim is to encourage students from 14-18 years old to look at how sensors can be used to collect geophysical data and integrate it together to give a wider understanding of physical phenomena. A second aim is to provide useful data on the spatial variation of the magnetic field for analysis of geomagnetic storms, alongside data from the BGS observatory and SAMNET variometer network. The system uses a Raspberry Pi computer as a logging and data transfer device, connected to a set of miniature fluxgate magnetometers. The system has a nominal sensitivity of around 1 nT RMS (~1 part in 50,000) in each component and is relatively low-cost at about £250 per unit. We intend to build 10 systems initially. In this poster we show results from the build and testing of the sensor and examples of recorded horizontal field