This study examined the impact of High Stakes Testing (HST) on the practice of teachers and administrators in New York schools from the perspective of education consultants. The results of annual state tests had high stakes consequences for students, teachers, principals and schools. Poor test results over time meant that teachers and administrators might be redeployed, dismissed and schools closed. Teachers and administrators often discussed HST and its impact on their work, with some endorsing and others vehemently challenging its ‘validity’ and utility. An investigation of the influence of HST on the work of teachers and school administrators in New York Schools was undertaken using a mixed methods approach. Data were collected through an online survey from 112 respondents and from semi-structured interviews conducted with 8 consultants. The quantitative research data were analysed with descriptive and inferential statistics and qualitative data was evaluated using thematic analysis. Foucault’s concept of ‘governmentality’ framed aspects of the study and thematic analysis of results suggested that the HST context was directed at accountability measures rather than directly improving student learning outcomes. Findings further indicated that high stakes testing was linked to reduced teacher control in instructional planning, a narrowing of the curriculum related to non-tested subjects and increased use of test preparation activities during classroom instruction. The annual state tests were associated with a decrease in teacher collaboration as project work in core subjects declined and instruction in non-state test subjects was reduced or marginalized. Teachers and administrators experienced increased stress and reduced work satisfaction as the instructional focus narrowed with increased test preparation activities. This initial study indicated that the unintended consequences of initiatives such as HST need to be critically interrogated if teachers and administrators are to work more effectively to improve student-learning outcomes.