The research reported in this paper explored the implementation of a language-in-education policy in post-Soviet Kazakhstan, also known as trilingual education reform. Drawing on interviews with teachers and school administrators, the paper comparatively examines how the teaching of Sciences through the medium of English was implemented across two different educational contexts in one country. The analysis shows that different processes were undertaken to involve teachers in the reform and get them to implement change. The network of elite Intellectual Schools approached language planning by exerting positive pressure, offering ongoing capacity building, emphasising core pedagogy, and providing opportunities for 'learning in context,' whereas the policy in the context mainstream schools was characterised by excessive speed, fragmented solutions and the failure to provide micro-level policy actors with sufficient tools to implement change. The paper argues that piloting results should be carefully considered before scaling up the reform to a larger context. Finally, the paper suggests core premises of educational change should inform language planning and policy decisions.