During their training, future teachers usually learn the subject matter of science. However, they are largely left on their own when it comes to figuring out how to teach this subject matter, that is, how to find appropriate pedagogical forms. In this article we present a model of collective teaching and learning, which we term coteaching/cogenerative dialoguing, as a way to build deep learning of science concepts while learning about alternative ways to teach the same subject matter. As praxis, coteaching brings about a unity between teaching and learning to teach; cogenerative dialoguing brings about a unity between teaching and researching. Both are potential sites for deep learning. We articulate coteaching/cogenerative dialoguing in terms of activity theory and the associated first-person research methodology that has been developed by critical psychologists as a method of choice for dealing with the theory–praxis gap. Our detailed case study highlights opportunities of learning subject matter and pedagogy by university professors who participate in coteaching/cogenerative dialoguing in an urban high school. © 2002 Wiley Periodicals, Inc. J Res Sci Teach 39: 253–282, 2002