Critical thinking ability is one among the life skills enlisted by the World Health Organisation. Citizens who can think critically are the need of the nation. The new era warrants persons who can think and evaluate the information correctly. It is the duty of education to inculcate the skill of critical thinking in the students, the future citizens. The study was conducted using the normative survey method. The sample for the present study consisted of 640 secondary school students from different schools of Palakkad district. A tool, namely Critical Thinking Ability Test for Higher Secondary School Students was constructed and standardized by the investigators for the study. The study investigated the influence, the effect of gender, type of management and the optional subject on the critical thinking ability of higher school students. Statistical measures such as t-test and ANOVA were used to analyze the data. The result of the analysis shows that a significant difference exists in the mean scores of critical thinking ability with respect to gender, type of management and optional subjects of students.