The school principal, Andjelka Dukat, said that classical education provided a broad and deep knowledge of the roots of European spirituality, culture and civilisation.
"Croatia has a centuries-long tradition of using the Latin language and the continuity of humanistic education," she said.
Zagreb University Chancellor Aleksa Bjelis said that Zagreb's classics-programme secondary school was unavoidable in the development of Croats' national awareness.
The seminar, held under the auspices of the Croatian parliament, was also addresed by the head of the Zagreb Archdiocese Gymnasium, Ivan Gretic, and the dean of the Jesuit Faculty of Philosophy, Ante Misic.
Addressing the event, Zagreb Archbishop Josip Bozanic said that culture today was based on the Greek, Latin, Jewish and Christian cultures and that classical education enabled a dialogue with other cultures on an equal footing.
The Apostolic Nuncio to Croatia, Francisco Javier Lozano, said that gymnasiums founded by the Jesuit order enabled the transfer of religious, intellectual and moral legacy to today's generations.
Urging dialogue among cultures, he called on the present to read Pope Benedict XVI's speech in Regensburg.
The Zagreb meeting was also addressed by the head of the Congregation for Catholic Education at the Holy See, Cardinal Zenon Grocholewski.