This article reports a multiple case study that explores the potential impact of Japan's national curriculum for senior high school English as a foreign language (EFL), specifically in relation to the integration of grammar teaching with communicative work, a key component of the curriculum and an area globally underresearched in high schools. The beliefs and practices of four Japanese EFL teachers from different public and private high schools were investigated over a 16-month period. Quantitative data were collected from four classroom observations, while qualitative data were gathered through a preliminary beliefs questionnaire, 10 teacher journals, and postobservation and semistructured interviews. Extending the EFL literature to date, this article draws on the theory of planned behavior as an analytical framework to reveal a complex interrelationship between the various attitudinal, social, and contextual factors that would both obstruct and facilitate teachers' integration of grammar teaching with communicative work. Importantly, the findings also bring to light a number of concrete ways in which some teachers manage severe social and other contextual pressures to successfully achieve integration, despite the influence of university entrance examinations that emphasize reading.