The concept of academic self-efficacy, which refers to Albert`Bandura`s self-efficacy theory, is an important factor in students` academic achievement. In this thesis we attempted to develop a research tool for assessing academic self-efficacy. The theoretical part focuses on general definition of self-efficacy and specific characteristics of perceived academic self-efficacy. The empirical part deals with the development of the questionnaire, with verification of its psychometric characteristics and determines its validity. The questionnaire was tested on a research sample of 611 students of five Prague secondary schools, aged 15 - 19. The findings indicate that the developed assessment tool is reliable, has good psychometric qualities and satisfactory validity, and is applicable in school practice. The research has also revealed interesting relations between academic self-efficacy and other variables such as gender, age or demanding school situations experienced by student. Keywords: self-efficacy, academic self-efficacy, academic motivation, high school students, assessment, The Study Experience Questionnaire