Environmental education programs aiming to enhance children's environmental attitudes in a pro-environmental direction require background information, such as age and sex differences, to ensure appropriate design. We used the 2-MEV model with its domains "preservation" and "utilization" of nature to assess a four-day program at an educational field center with students 9-10 and 11-13 years of age. A pre- and post-retention test design revealed younger students to be more responsive concerning positive attitude shifts than older students, whereas the sexes were equally influenced. Program developers should consider that education has a stronger effect on young children's environmental attitudes.