Critical thinking refers to a mode of thinking--about any subject, content, or problem--in which the thinker improves the quality of his or her thinking by skillfully analyzing, assessing, and reconstructing knowledge. This study evaluates the critical thinking skills of private and public high school students in Kuwait and examines the practices related to critical thinking skills that are employed by schools. This study relied on a quantitative method that employed the Watson-Glaser Critical Thinking Appraisal (WGCTA) to test critical thinking skills among students, and used a questionnaire based on the conceptual framework proposed by Paul and Elder (2012) to evaluate critical thinking practices in school. The questionnaire was distributed to 273 private and 258 public school students. The WGCTA was administered to 26 private and 39 public school students. An independent T-test analysis concerning the WGCTA showed that the overall WGCTA mean with regard to the inference subskill was low in both the public and private schools. The questionnaire responses, however, revealed a significant difference in raising questions and solving problems and communication skills in favor of public schools, while the scores on the measures of critical thinking were significantly higher in private schools.