The purpose of this study was to investigate the effectiveness of EarthComm implementation in the U.S. high schools in terms of demographic background including school size, urban/rural area, and teachers' teaching experiences. In addition, this study examined impact of students' higher-order thinking skills by using the visions of National Science Education Standards. Two modular of the EarthComm curriculum were used for this purpose with thirty one teachers and around thousand students involved across four states. Findings were that EarthComm did not significantly impact student achievement differentially in schools of varying sizes and school location, i.e., urban and rural areas. The years of teaching experiences did not impact student achievement scores for Module I but did significantly impact for Module II. It is noted that the two results seemingly conflict with each other similar to other research findings (Ferguson, 1998; Yager et al., 1988). Student higher-order thinking skills, on the other hand, were significantly improved as a result of studying with EarthComm. Implications were discussed at the end of the paper.