The article deals with educational peculiarities, which highlight modern educational priorities, of the content of textbooks for classes 9 and 10 prepared during the current three years by individual Lithuanian authors. Applying content assessment analysis, didactic principles of preparation of textbooks were examined, and forms of educational expression of generic competencies (ability to learn, cognition, communication, use of ICT and other) in textual, visual, practical and other materials of these learning aids were revealed.During the research it was established that the key point of the content structure of modern textbooks is assistance to the student and the teacher. To achieve the set aim textbooks contain not only knowledge, but they also advise, encourage, motivate, indicate a learning direction, provide possibilities for students to check and evaluate their achievements themselves.Modern didactic principles are reflected in the content of textbooks in different forms which are accessible to students. One of them, i.e. a principle of accessibility, could be noted as it is revealed on the basis of the peculiarities of students‘ developmental cognitive psychology and logic; however, inborn or acquired special needs, learning styles of individual students are considered only in part. A principle of integrityis particularly distinct in the content of textbooks from the point of view of the subject, internal and socio-cultural integration. In the content of „Biology 9” and “Biology 10“, interdisciplinary integration is emphasized more. This educational principle is aimed at linking knowledge of different subjects by notional relationships. In the textbooks of „Bios“ series more attention is given to internal integration of the subject. It is guaranteed linking concepts and conceptions of the same subject by internal interrelations. Application of sociocultural integration aims at developing students’ general scientific conception. This principle of integration is expressed by linking concepts of ecology, healthy lifestyle, consumer culture or other areas with the biology subject content.Analysis of textbooks from the point of generic competencies demonstrated that this educational aspect is particularly distinct in the textbooks published in 2010–2012. In their content, it is aimed at developing generic competencies through certain sections, topics, tasks: ability to learn– “How to Study Biology”; the following rubrics are devoted for the developmentof a cognitive competency: “Science Report”, “Do it Practically”, “Laboratory”, “Method”;an ICT application competencyis developed by teaching how to use the opportunities provided by these technologies in searching, summarizing or submitting information, or processing the data of researches, tests and observations, examining or modelling phenomena. To achieve this aim, relevant Internet websites that can be used both in the classroom and at home are indicated; communication, initiative and creativity competenciesare developed through discussions of the tasks performed, debates, analysis and assessment of the results of the work, drawing conclusions.A social competencyis developed through the ability to socialize and cooperate, respect for the person, his rights and dignity. The content of the analyzed textbooks is characterized by a rather innovative biology education system, i.e. a constructivist approach to teaching (and learning) is evident, modern didactics and a provision of education (self-education) targeted to learning activities is emphasized. The mentioned learning activities involve: independent and active students’ learning, working in pairs or in groups, information search and its presentation, science research, vocational orientation.The material is presented in a form of problems, life situations encouraging critical thinking are created; the phenomena analyzed in topics are associated with the currently topical issues and presented according to the latest discoveries and technologies.