Аннотация: The article presents a study aimed at determining the possibilities of predicting the success of primary school graduates in basic school. Based on the material of the author's tasks "Exchanges", "Permutations" and "Comparison" at the end of the school year, diagnostics of the formation of meaningful mental activity of fourth-graders was carried out. 52 schoolchildren participated in the study. At the first stage of the study, children solved a series of homogeneous problems of the task "Exchanges" in a visual-figurative form, at the second stage - a series of problems of the task "Permutations" in a subject-active form, at the third stage - a series of problems of the task "Comparison" in a verbal-symbolic form. As a result of the noted diagnostics and on the basis of feedback from teachers teaching these subjects in the fifth grade, it was determined that the success of the implementation of the noted tasks characterizes the level of readiness of the fourth-grader for further education. Thus, children who successfully completed all three tasks have a high level of readiness for studying in the middle grades of school, children who successfully completed only two tasks: "Exchanges" and "Permutations" have an average level of readiness, and children who successfully completed only one task - "Permutations" - a low level of readiness.