Given the multitude of attitude scales, we examined the relationship between the 2-Major Environmental Values model (2-MEV) and the New Environmental Paradigm scale (NEP) based on a 6585 child sample over a 9-year period. The students participated in a three-day outdoor earth education program at field centers in three different US states (Arizona, Pennsylvania, and Louisiana). We further investigated the scales’ sensitivity to program effects, relating cognitive achievement and attitude with respect to a pro-environmental indicator of behavior (Y key). The NEP and Preservation correlated highly, while the subscales Utilization and Preservation showed a strong inverse relationship. Based on further reliability and validity scores, and in line with the literature, this pointed to a unidimensional Preservation of Nature scale as a concise attitude measurement. In structural equation modelling, Preservation related to knowledge gains and the Y key, and effects from Preservation on knowledge held true for all three states. This suggests Preservation as one factor influencing cognitive achievement and environmentally conscious performance. Regarding program effects, the Earthkeepers program seemed to induce pro-environmental shifts based on knowledge gains and attitude changes (Preservation increasing and Utilization decreasing). Pro-environmental shifts were most prominent for those who received the Y key.