In the context of increasing ethnocultural heterogeneity of student groups caused by migration processes, globalization and demographic changes in the regions of the Russian Federation, pedagogical approaches aimed at forming the culture of interethnic interaction among high school students are becoming particularly significant. Ethnocultural practices, representing a set of activity-oriented forms of mastering ethnocultural heritage through participation in ritual reconstructions, preparation of joint projects, mastery of traditional crafts and folklore, conducting ethnographic expeditions and intercultural communication trainings, demonstrate high potential for the integrated development of the cognitive, emotional-value and behavioral components of this culture. The cognitive component provides knowledge about cultural diversity and communication mechanisms, the emotional-value component contributes to the development of empathy and tolerance, while the behavioral component manifests itself in readiness for constructive interaction in a polyethnic environment. The implementation of a comprehensive program of such practices in educational organizations of the Republic of Tatarstan and the Samara Region involving 214 students in grades 10-11 revealed a pronounced positive trend in the experimental group compared to the control group. Initial diagnostics showed the predominance of medium and low levels of development of the components, with the greatest difficulties observed in the behavioral sphere (about 41% at a low level). After the phased implementation of six program modules (ethnographic mini-expeditions, project-based research activities, craft workshops, discussion clubs, ethnocultural festivals and communication trainings), the proportion of high school students with a high level of the cognitive component increased from 14,4 to 36,4%, the emotional-value component from 22,0 to 45,7%, and the behavioral component from 16,1 to 39,0%, whereas changes in the control group did not exceed 3.1 percentage points. Students’ subjective assessments highlight the particular effectiveness of integrative forms such as ethnocultural festivals, which received the highest overall significance score (8.43 out of 10), in contrast to workshops that were rated highly on emotional impact (8.7) but lower on practical significance (5.8). Correlation analysis confirmed the differentiated impact of the modules: project-based research activities demonstrate a strong association with the cognitive component (r = 0.71), craft workshops with the emotional-value component (r = 0.73), communication trainings with the behavioral component (r = 0.74), while festivals provide balanced high correlations across all components (average r = 0.643). Measurements of interethnic tolerance recorded an increase in the integral indicator in the experimental group by 17.1 points (from 51,6 to 68,7 or 33,1%), with the most pronounced dynamics in the affective and conative subscales, whereas the control group showed an increase of only 2.2 points. The obtained data illustrate the synergistic effect of modular integration of ethnocultural practices, which contribute not only to raising the average level of the culture of interethnic interaction but also to group consolidation, reduction of individual differences and formation of stable models of tolerant behavior. This is particularly relevant for polyethnic educational environments and can serve as a basis for developing regionally adapted programs of multicultural education that ensure the harmonious coexistence of representatives of different ethnic groups in modern society.