Complex sentence: Previously, he was an "agrégé" professor of sociology in the Department of Social Sciences at the École Normale Supérieure in Paris and also a researcher at Institut de recherche interdisciplinaire sur les enjeux sociaux.
Split into simpler sentences: Previously, he was an "agrégé" professor of sociology in the Department of Social Sciences at the École Normale Supérieure in Paris. He is also a researcher at Institut de recherche interdisciplinaire sur les enjeux sociaux.