Ocean acidification (OA) has been called climate change's evil twin for a reason. Increased levels of carbon dioxide, caused by humans burning fossil fuels, are not only causing a rise in global temperature but are also having adverse impacts on marine ecosystems. In the lesson presented in this article, students conduct investigations using models to explain how increases in CO[subscript 2] affect ocean pH and examine the impact of ocean acidification on the ability of oyster larvae to produce shells. The lesson is organized around an overall driving question and two more focused, investigative questions. The lesson has been designed for, and implemented in, both the middle and high school levels, and takes less than 250 instructional minutes. An extensive teacher's guide for the lesson is available and contains the activity setup and facilitation information, readings for teachers and students, scaffolding suggestions, student handouts, and anticipated student responses. While many OA activities for students focus on its effects on adult marine organisms, such as weakening and dissolving of shells, this lesson highlights how OA impacts the ability of larval oysters to build their shells, a critical process that must occur in the first 24 hours of life. This lesson was explicitly designed to engage students in three-dimensional learning, as called for by the "Next Generation Science Standards" ("NGSS"; NGSS Lead States 2013).