The Children's New Ecological Paradigms scale was originally developed for children ages 10-12 and was presented as valuable for comparing that age group with older participants. This study uses cognitive interviews and measurement invariance testing to investigate how well the scores maintain the same meaning between these two age groups. The qualitative and quantitative results were consistent in revealing that at least 20% of the items function differently than expected when we use it for this purpose. The findings revealed similarities with critiques of the adult NEP and questioned the validity of the use of this instrument in its present form.