<p>The textbooks and course syllabi play an essential role in helping teachers and learners achieve the expected learning outcomes. This study aims to unlock cognitive learning objectives in Khmer textbooks and course syllabi by revising Bloom’s taxonomy across disciplines at primary schools. A purposive sampling method was utilized to select textbooks and syllabi from the primary school curriculum published between 2007 and 2018, focusing on the Khmer language, Mathematics, and Science. Based on cognitive learning objectives, the quantitative content analysis methodology was applied to Khmer textbooks and course syllabi with Khmer language, Mathematics, and Science at the primary level. Inferential statistics were used to examine the distribution of lower-order and higher-order thinking skills between Khmer language, Mathematics, and Science in both textbooks and course syllabi at the primary level. The results of this study revealed significant differences in the distribution of lower-order thinking skills and higher-order thinking skills between primary textbooks and syllabi across disciplines. While course syllabi exhibited higher-order thinking skills more frequently than textbooks, they predominantly focused on low-order thinking skills. Thus, the results of this study will be considered by the Ministry of Education, Youth and Sport (MoEYS), educators, curriculum designers, educational partners, and stakeholders, who aim to improve the education system by revising Khmer textbooks and course syllabi across disciplines.</p>