Indonesian government policy has emphasised Critical Thinking development in secondary school students to position the nation for better engagement with global concerns, including the Industrial Revolution 4.0. A vehicle of choice to achieve this Critical Thinking development is English as an Additional Language in Secondary Schooling. This article presents a qualitative study that investigated the characteristics and prevalence of Years 10, 11 and 12 Critical Thinking in English listening and speaking tasks in an Indonesian high school. Data were generated through sustained engagement with one class in each year level, providing rich and detailed classroom data. These data were analysed with a conceptual framework of Critical Thinking in English Listening and Speaking to determine the characteristics of student Critical Thinking. Frequency counts of the characteristics yielded the prevalence of Critical Thinking in the period of engagement with each class. The point of intersection between Critical Thinking policy and its implementation demonstrates the congruence and dissonance between the actualised student Critical Thinking and teacher documents. Results showed that the characteristics and prevalence of Critical Thinking were fundamentally different for each year group, in large part due to the differences in teacher facilitation of Critical Thinking, despite, or because of, the overarching policy directives.