Rainey began his career in higher education by teaching education at Austin College for three years before receiving his masters and doctorate at the University of Chicago. After receiving his doctorate, he taught for three years at the University of Oregon, then became the president of Franklin College in Indiana from 1927-1931 before becoming the director of the American Youth Commission of the American Council on Education. From 1931 to 1935, he was the president of Bucknell University. Subsequently, he served as director of the American Youth Commission of the American Council on Education for four years.
