The purpose of this empirical study was to present a detailed description and interpretation of what happens in schools to beginning teachers who are prepared to enact reform-based practices in mathematics and science. The focus was on a select sample of graduates from the Maryland Collaborative for Teacher Preparation [MCTP], a statewide reform-based undergraduate teacher preparation program funded by the National Science Foundation. Interpretative research methodology was used to conduct a cultural case study of the beginning teachers' first 2 years of practice (first year, N = 5; second year, N = 3). We documented differential experiences and perceptions of the beginning teachers from both inside (emic) and outside (etic) perspectives. Documented discussion centered on an analytical framework suggested elsewhere. Findings were framed in two components: the individual's intentions, needs, and capabilities; and the institutional demands, affordances, and constraints. The major insight was that the beginning teachers' perception of their school culture was a major factor in whether reform-aligned mathematics and science teaching was regularly implemented by the beginning teachers. In instances where the beginning teachers' perceived that their school cultures offered a lack of support for their intent to implement reform-based practices the beginning teachers exhibited differing social strategies (resistance, moving on, and exit). Therefore, to sustain reform (and, by extension, to retain beginning mathematics and science teachers), a key implication is to place additional attention on the use of the school culture perspective to improve teacher preparation and induction experiences. © 2004 Wiley Periodicals, Inc. J Res Sci Teach 41: 720–747, 2004