This study investigates learning experiences of school children (G4 – G6) studying in Nakhon Ratchasima Province who attended school field trip to the Phimai Historical Park (PHP), the biggest Khmer Sanctuary in Thailand, which is a popular tourist attraction and important learning resource for school children. It is focused on what and how young children learn from their informal education and field trip. Significant interpretation objectives and suitable knowledge themes for young learners are examined in order to establish heritage understanding including lifelong learning as it is emphasized in the Reform of National Education system of the 15-year Free Education. The picture of how the school children were prepared for their historical site visit was established in order to understand the value, extent and effectiveness of the learning experience. School curricula and texts about Phimai and related topics were interrogated. The research method is based on empirical surveying, observation and in-depth interviewing to explore the learning experiences during the visits by students to the PHP. Evaluations were obtained from responses to surveys. The study uncovered large numbers of positive results, providing direction for how to arrange young learners for historic site visits. Both teachers and students mentioned that Social Studies, especially History, provided the main themes for the field trips. However, although the school field trips would benefit students learning in the classroom, the data showed that the teachers were limited in recognizing their role in connecting the field trip with the school curriculum and the lessons provided. The structure of the field trips was guide-centered. A worksheet provided by the school was only a task for students to submit in relation to the site visit. A demonstrable communication gap between teachers and guides about effective interpretation for children was observed. This gap, and the limited involvement by some teachers in interpretation, limits the effectiveness of the learning experience for some students.