The article examines the actual problem of the discrepancy between, on the one hand, the society's demand for the formation of functional literacy among schoolchildren through cross-subject training for the successful adaptation of school graduates in a complex world, and, on the other hand, the insufficiently developed practice of cross-subject training in general education organizations. In accordance with the identified problem, the purpose of the research proposed in the article is to substantiate the methodological approach to the organization of cross-subject training for the formation of functional literacy of students in schools of general education institutions and its testing on the example of cross-subject tasks. The research was based on a systematic approach that allowed authors to imagine the formation of functional literacy based on cross-subject learning with the performance of certain functions and on the basis of the most suitable forms of organization of the educational process for these tasks. The novelty and peculiarity of current solutions are the development of organizational forms of cross-subject training with reference to functional literacy and using such forms of training organization as project-based training, case-based training, and problem-oriented training. The authors' experience in the development and use of cross-subject tasks is described, and examples of problems that the author's developments are aimed at solving are given. The article also offers a description of the experience in using project-based learning, problem-based learning, and the case study method in developing and solving cross-subject tasks for students. The results of the study may be useful for representatives of general education organizations that implement different forms of functional literacy training using cross-subject tasks.