In 1884 he entered the Marist novitiate at Paignton, England, and in 1886 he was awarded BA at the Royal University of Ireland in mathematics and science.
For the following two years he taught at his old school in Dundalk, during which time he wrote a textbook, Natural philosophy for junior students, covering a variety of scientific topics including mechanics, hydrostatics, pneumatics, gravity and motion.
Kennedy continued his scientific pursuits and gave public lectures illustrated with lantern slides.
Kennedy gave evidence before the Education Commission of 1912, and while at St Patrick's College enthusiastically promoted the study of science.
One of his pupils, James Bronte Gatenby, in 1920 became the first recipient of a DPhil degree from Oxford University, and was later professor of zoology and comparative anatomy at Trinity College Dublin.