Preparing students for informed democratic citizenship by learning about contemporary political and social issues requires the ability to critically evaluate online data visualisations. This study examines 25 social studies teachers' perceptions of online data visualisations as informational resources for teaching, and how these perceptions influence their reading of online data visualisations. The goal is to examine teacher understandings of the influence of fake news, how they understand issues of bias and credibility for data visualisations, and how their perceptions influence their interpretive practices. The study employed semi-structured interviews and a think aloud protocol. The think aloud involved the reading and analysis of a single online data visualisation. The findings provide insights into the ways that social studies teachers think about the role of data visualisations and online information in social studies education, their challenges to read and interpret online data visualisations, and implications for teaching.