Following his graduation from St. Stanislaus Kostka grammar school, Rostenkowski attended St. John's Military Academy in Delafield, Wisconsin, where he earned letters in baseball, football, basketball and track. After graduating from St. John's in 1946, he enlisted in the United States Army and served for two years as a private with the Seventh Infantry Division in Korea. In 1949 he tried out for the Philadelphia Athletics, but his father convinced him to give up his dream and come home, as his mother was losing a battle with cancer. After her death, he enrolled at Loyola University in Chicago.