Most students from the École Normale Supérieure went on to become school teachers but Lions, and his friend and fellow student Bernard Malgrange, decided that they wanted to become university teachers.
Karamihan sa mga mag-aaral mula sa École Normale Supérieure pumunta sa paaralan upang maging mga guro ngunit Lions, at ang kanyang mga kaibigan at mga kapwa mag-aaral Bernard Malgrange, nagpasya sila na kinakailangan upang maging unibersidad guro.