Our society is currently having serious debates about sources of energy and global climate change. But do students (and the public) have the requisite knowledge to engage these issues as informed citizenry? The learning-progression research summarized here indicates that only 10% of high school students typically have a level of understanding commensurate with that called for in the "Next Generation Science Standards." The learning-progression research shows how most students fall short of being able to trace matter and energy through carbon-transforming processes such as photosynthesis, respiration, and combustion that are at the center of analyses of energy use and global climate change. We discuss the more typical types of understanding that students develop and their implications for teaching.