Abstract: In this article, the author seeks to reconsider the chronology of the dialogue «Euthyphro», which is usually considered to be Plato's earliest dialogue. Having shown the incongruity of the traditional early dating, the author, proceeding from the idea of the genre evolution of Plato's work, places the dialogue among the school ones, written against the background of the composition of Plato's «Laws». In order to corroborate the thesis, the author refers to the early works of Aristotle, who had a significant role in Plato's Academy. On the basis of the «Topics» and «Sophistic Refutations» it is shown how Aristotle reflected in his works the realities of school disputations, as well as work on certain problems reflected in the «Laws» and elaborated in school dialogues. The author substantiates the thesis that Aristotle's «Topics» and «Sophistic Refutations» reflect not the previous disputes of sophists, but the state of sophistic schools, contemporary to Aristotle. Taking into account the focus of Aristotle's early works on his and Plato's opponents, the Megarics, the author suggests that the aporetic character of school dialogues is a reflection of the Megarics' eristics. The direct parallels with the early works of Aristotle permit us to see in the dialogue «Euthyphro» an example of academic discussion of a certain theme of the «Laws» – the relationship between justice and piety, the author of which was one of the members of the Academy, who was inspired by Plato's «Theaetetus» and in some respects was in disagreement with his teacher.