Katz originally studied agriculture at the Ahava youth village until 1944, while simultaneously through intense self-study, completing his matriculation in an outstanding manner. As a result, he was awarded a scholarship by the British Mandatory Government but chose to study science at the Hebrew University of Jerusalem from 1946 until 1947. During the course of his studies, he began working on the treatment of delinquent youth in a poor neighborhood of Jerusalem. On the eve of the 1948 Arab–Israeli War, he joined the Israel Defense Forces (IDF) serving in the Intelligence Services.