This study examined the integration of technology enhanced formative assessment (FA) into teachers' practice. Participants were high school physics teachers interested in improving their use of a classroom response system (CRS) to promote FA. Data were collected using interviews, direct classroom observations, and collaborative discussions. The physics teachers engaged in collaborative action research (AR) to learn how to use FA and CRS to promote student and teacher learning. Data were analyzed using open coding, cross-case analysis, and content analysis. Results from data analysis allowed researchers to construct a model for knowledge skills necessary for the integration of technology enhanced FA into teachers' practice. The model is as a set of four technologies: hardware and software; methods for constructing FA items; pedagogical methods; and curriculum integration. The model is grounded in the idea that teachers must develop these respective technologies as they interact with the CRS (i.e., hardware and software, item construction) and their existing practice (i.e., pedagogical methods, curriculum). Implications are that for teachers to make FA an integral part of their practice using CRS, they must: 1) engage in the four technologies; 2) understand the nature of FA; and 3) collaborate with other interested teachers through AR.