Abstract
This study evaluates the impact of an augmented critical thinking (CT) curriculum on the development of CT skills among 9th grade students in Saudi Arabia. Saudi Arabia recently introduced a national critical thinking course as part of its Vision 2030 education reforms, aiming to shift students away from rote learning toward analytical, evidence-based reasoning. While the curriculum represents an important policy commitment, little is known about whether it effectively develops students' CT abilities in practice. We ground our work in List's (2022) CT Hierarchy, which defines critical thinking as the ability to reason empirically and abstractly, and recognizes that these skills develop progressively: from intuitive, bias-prone thinking toward more deliberate, reflective reasoning. Building on this framework, we developed a structured CT assessment and an augmented curriculum module for 9th grade that intensifies the existing national course with active learning methods, including logic exercises, claim-evidence-reasoning tasks, and metacognitive reflection. Using a randomized controlled trial across schools in Makkah and the Eastern Province, we measure whether students who receive the augmented curriculum show greater gains in CT scores relative to those receiving the standard curriculum. Our assessment captures performance across four cognitive domains: correlation vs. causation, logical reasoning, mathematical and statistical thinking, and cognitive bias. We also examine variation by gender, and baseline CT level. Results will inform curriculum policy and teacher training at scale, with implications for how CT can be effectively taught within national education systems.