This longitudinal study examines growth in teacher knowledge as measured by two popular assessments--Learning Mathematics for Teaching (LMT) and Diagnostic Teacher Assessments in Mathematics and Science (DTAMS). Using data collected from 24 teachers, we compare the extent to which each assessment captured teacher learning during a K-8 mathematics content/pedagogy hybrid course and a general mathematics content course. Teachers made large gains on both measures, but the LMT better captured gains made during the hybrid course, whereas DTAMS better detected gains during the mathematics course. Patterns in teacher performance suggest substantive differences between specialized mathematical knowledge for teaching and everyday mathematics knowledge. The theoretical and practical implications of these findings are discussed.