Kowalewski's father did not have a large income, but gave his sons a good education at home. This was favored by the fact that the uniate priest enjoyed traditional economic privileges, had a certain income from demands for correction, and could also keep tenants or serfs on his lands. According to tradition, dignity and service passed to one of the sons, others made a secular career, while daughters were married only to priests. Józef was sent quite early to the Svisloch gymnasium, which was under the care of the Vilnius University, where his brothers Julius and Theodosius were already studying. The gymnasium quickly gained a reputation as one of the best Polish educational institutions, its founder, Count W Tyszkiewicz, took care not only of organizing the educational process, but also of the gymnasium's leisure time, education was free, but the parents of the students contributed money to the maintenance of educators-supervisors , who were recruited from the students of the same gymnasium who completed the full course. There are certain discrepancies in the chronology of Józef Kowalewski's stay in the gymnasium. Polish and Belarusian sources call the initial year of his studies 1808 or 1809, there are doubts that in 1817 he completed the full course. Kowalewski showed considerable abilities in the humanities and wrote bucolics in the classical style. During the French invasion Svisloch was occupied by the Saxon units of Schwarzenberg, looters plundered the gymnasium, and Józef Kowalewski lost his chest along with all his poor property. The “loss” of one or two years is probably due to the fact that Józef served as a home tutor, which was widely practiced. He chose the university as the place of his further stay.