Drawing on a study of new forms of educational privatization, this article examines how ideas from institutional theory can be useful in analyzing the complex dynamics behind interim assessment technologies. The study was based on qualitative research methods and included interviews, a small-scale questionnaire, participant observation, and analysis of public and financial documents. As defined here, interim assessment technology is the software that is sold to schools and districts in order to gauge students' progress toward high-stakes tests and to comply with the testing and reporting requirements of the No Child Left Behind Act of 2001. The design and implementation of these assessment technologies reflects the complex pressures on schools and districts--to be more efficient, to be more compliant, and to be more equitable. I argue that in understanding the consequences of these technologies, we need to pay close attention to interactions between private firms and public agencies. Examining these interactions is important--for drawing attention not only to what is changing in public education but also to what is not. Private vendors can design sophisticated technologies for generating, storing, and reporting test score data. These technologies can be adopted system-wide. However, from the perspective of school staff, privately designed services and products still can seem very disconnected from the actual challenges of improving instruction. (Contains 3 figures, 1 table, and 4 footnotes.)