The article presents the results of a study of the functional literacy of students in biology of grades 9th. The methodology for assessing the functional literacy of 15-year-old students of the international PISA program is used. Approbation was conducted with the test tasks of different level of complexity for an assessment of natural-science functional literacy. The results of the research showed that in the process of preparing students for the exam it is necessary to conduct systematic work directly with the test tasks and at the same time to develop and strengthen knowledge and skills of the basic level.