Professor Yopp's interests include proof and reasoning teaching and learning and the knowledge needed for effective mathematics instructional coaching in elementary and middle grades. He is the co-principal investigator on the 3.5 million dollar NSF-funded DRK-12 Grant Examining Mathematics Coaching, EMC. He has published in the Journal for Mathematical Behavior, Investigation in Mathematics Learning, Mathematics Teaching in the Middle School, Teaching Children Mathematics, the MAA Focus, and Linear Algebra and Its Applications, among others.