In 1886 he entered the high school Athénée Royal d'Ixelles and studied there until his graduation in 1891. Twice during his time at this school Constantin won a prize as the best mathematics student in Belgium.
Sa 1886 siya ipinasok ang mga mataas na paaralan Athénée Royal d'Ixelles-aral at may hanggang sa kanyang graduation sa 1891. Dalawang beses sa panahon ng kanyang panahon sa paaralang ito Constantin napanalunan ng isang premyo bilang pinakamahusay na matematika mag-aaral sa Belgium.