This paper addresses the value of effective, significant heritage education pedagogic activities and tasks when teaching heritage topics in history and social science lessons. Heritage pedagogy needs to challenge students' preconceptions about their heritage and encourage learning about it: the investigation, interpretation and provenance of its sources and its significance. Our article is based on a research project in Portugal and Spain to evaluate the impact of heritage education pedagogy on students' historical understanding and their development of national identity. This paper's research involved secondary school students in northern Portugal. To assess their understanding of heritage, they completed a questionnaire at a heritage site with a focus on buildings, archaeological remains and museum artefacts that related to aspects of national history studied in schools. Analysis of their questionnaires revealed the relationship between students' interpretation of the heritage site's historical evidence and their historical consciousness. Although most students treated the heritage site buildings, remains and artefacts as sources of factual information about a fixed, given and largely unremembered past, several students questioned, hypothesized, and treated the sources as historically contextualized evidence that dovetailed with their existing historical knowledge. Contextualized interpretation is essential to historical understanding; accordingly, students studying heritage should be trained to analyse its historical sources in relation to their historicity. More generally, teaching about heritage should give students opportunities to challenge preconceptions they hold about it, and to learn how to deal with different, contrasting, difficult and controversial interpretations of heritage topics and sites in their historical contexts.