She studies students’ learning, focusing on algebraic reasoning, generalization, and proof. Ellis received her doctorate from the joint program at the University of California, San Diego and the San Diego State University. She also holds a master’s degree in mathematics. Prior to her appointment at the University of Wisconsin, she spent a number of years teaching math at the middle school and high school levels in California. In her current position she enjoys working with pre-service and in-service mathematics teachers at the sixth- through 12th-grade levels.