The theory and practice of specialized training in national school in the second half of the 19th - 20th centuries have been researched. The tendencies for specializing national secondary education have been summarized on the scientific and theoretical level. Scientifically-grounded periods of specialized training in the history of the national school for years 1849-1998 have been suggested: I - the period of specialized secondary education in Ukraine in empire time (1849-1916): the first stage (1849 - late 19th century), the second stage (early 20th century), the third stage (1915-1916); II - the period of the development of the idea of specialized training in national school during the liberation struggle (1917-1919); III - the period of introduction of specialized training in the Soviet high school (1920-1987): the first stage (1920-1927), the second stage (late 1920-1940), the third stage (1952-1964), the fourth stage (1966-1970), the fifth stage (1984-1987); IV - the period of the implementation of the ideas of specializations of academic trend in post-Soviet secondary school (1988-1998). The reasons and purposes for introducing specialized training in national school in the second half of the 19th - 20th centuries have been discovered; the factors determining this process have been identified: the need to preserve the dependence of education on the learners' social background; the need to direct the education of a particular student considering his abilities and interests; state and social requirements for training future specialists of a particular trend. The author determined and characterized the existing models of specialized secondary education in Ukrainian schools in the second half of the 19th - 20th centuries (different types of schools; furkatsiya in senior classes in general schools, the opening of additional professionally-oriented classes or courses, the identification of high school as professionally-oriented, the opening of boarding schools specializing in learning particular subjects; the organization of extracurricular activity through students' societies; vocational training in high school; the introduction of optional subjects; the opening of schools specializing in learning particular subjects; the combination of high school education and vocational training through interschool vocational training institutions, enterprises, school workshops, etc.; classes with intensive study of one or more subjects, specialized classes preparing for entering a particular institution of higher education). The main achievements of scholars in the issues of national specialized school education have been summarized in the thesis. The results and difficulties of differentiation in general education schools have been analyzed. Time-tested experience is considered to be a major achievement in this field. It includes: the existence of various types of general secondary schools operating in accordance with the state policy and ideology, though differ by trends, by the amount of knowledge gained by the students, by the organization of the education process; the introduction of practically oriented specializations which preserve the obligatory knowledge within a unified, ideologically biased secondary school (upper grades differentiation for industry fields, technical groups, the introduction of industrial training and interschool vocational training); the introduction of specialized education of academic trend, with the subjects of general knowledge maintained (high school differentiation, specialized schools and classes with intensive study of core subjects, optional classes and courses), and with the syllabus divided into invariable and variable parts (specialized classes preparing for entering a particular institution of higher education, lyceums and gymnasia). The major drawbacks of specialized education of this period are: the absence of prior testing (national experiment), lack of necessary funding for introducing specializations and insufficient material base of most schools; low didactic and methodological support; lack of teachers' preparation to work in this field and lack of coordination between high school specializations and future labour needs. Scientifically and theoretically grounded tendencies for developing specializations in national high schools in the second half of the 19th - 20th centuries have been established. Their dependence on the social, political, economic and educational factors have been proved. The following tendencies have been mentioned: the dependence of aims, tasks and specialized high school arrangement on the political, social, economic and pedagogical factors; the dependence of the success of specialized education on didactic and methodological support and on the level of teachers' readiness to work in a specialized school; a limited number of hours to study the core subjects, while a large number of general educational subjects was maintained, but in the Soviet period all the subjects of general knowledge were preserved, thus bringing to students' overloading; the rigid structure of the curriculum, which limited the choice of educational preferences on the part of high school students; lack of unified requirements for the contents of core subjects and lack of correlation between general and specialized subjects; the identification of specialized training as prestigious, and as a criterion for social stratification. Little known and unknown archive documents as well as historical facts related to the development of specialized training in national school history have become a good addition to pedagogical science.