 He spent the first 12 years of that career in New York City and Washington, D.C., handling a variety of students, from fifth graders at Saint Mary's Parochial School in New York to the college students of the Manhattan College or La Salle College, teaching General Chemistry, Qualitative and Quantitative Analysis, College Mathematics, and the General Science, among others.In 1953 Duerr volunteered for mission service and was assigned to the Philippines, being first posted to De La Salle College.He was assigned to La Salle Academy-Iligan in 1958, the University of St. La Salle in Bacolod in 1969, and La Salle Green Hills in 1980.