AbstractPerformance in and perceptions of computational thinking (CT) are considered vital dimensions for comprehensively assessing CT skills of students. In this study, secondary school students’ CT performance and their perceptions were examined in terms of certain variables including gender, grade level, achievement and self‐efficacy. Casual‐comparative and correlational methods were used. The sample of the study consisted of a total of 328 fifth‐ and sixth‐grade (10–12 years old) secondary school students taking visual programming lessons. CT performance and perception tests were employed as data collection tools. The results show that CT performance of boys was higher than that of girls. A significant difference was found in both CT performance and perception depending on grades. The results show that achievement in math positively affected CT performance and perception. However, achievement in IT affected CT performance less than achievement in math. Implications are discussed in terms of theoretical insights, practices for improving CT skills in secondary schools and directions for further research. Practitioner notesWhat is already known about this topic Due to the complex structure of computational thinking (CT) in association with computers, cognition, learning and psychology, CT skills should be evaluated from a variety of perspectives. CT performance and perception are considered vital dimensions for comprehensively assessing students’ CT skills. What this paper adds This paper proposes a CT performance test and a CT perception scale for secondary school students to explore their skills in terms of certain variables including gender, grade level and achievements in math and information technology (IT) courses. This paper provides some evidence that CT performance of boys is better than that of girls. A significant difference was found in both CT performance and perception depending on grades. The results of the study show that math course achievement positively affected CT performance and perception. However, IT course achievement affected CT performance less than math course achievement. Implications for practice and/or policy CT performance is affected by different variables. Therefore, it may be beneficial to include specific topics in the curriculum that involve the use of more CT skills. Girls’ interest and participation in practices such as programming can be encouraged. Teachers should provide students with cognitive scaffolding to help them and to have them collaborate with each other during CT activities, especially at higher grades. IT course content should include systematic and comprehensive CT activities to improve students’ CT skills. We suggest developing and implementing a holistic curriculum combined with IT and math lessons to improve students’ CT performance.