A holistic education should nurture a range of skills that are essential for thriving in a fast-changing world, including higher-order thinking skills. These skills are deeply intertwined with knowledge and many in the assessment community agree they should not be assessed in isolation. Curricula structured around long-established subject disciplines and assessed via written examinations are often considered "knowledge rich". This article reports on how they also foster a range of higher-order skills that are important to students' futures. We conducted a systematic analysis of Cambridge International AS & A Levels in English Language, Geography, Physics, and Psychology. To suites of specimen examination papers, we applied a skills coding framework based on Marzano and Kendall's (2007) educational taxonomy, which encompasses problem-solving and metacognitive skills among other thinking skills. We incorporated additional codes for systems thinking components from an environmental sustainability framework. The analysis revealed a broad and rich coverage of higher-order thinking skills, as well as lower-order thinking skills such as retrieval, with variations across subjects. For example, while systems thinking is not mentioned in formal assessment objectives, it is present in Geography, Physics, and Psychology examinations. Although we did not explore this comprehensively, the study also suggested the examinations demand exam techniques that include metacognitive and problem-solving skills, further demonstrating higher-order thinking skills' integration within these qualifications.