Clarke was educated at the Model School in Marlborough Street, Dublin and Belvedere College, which he left in 1905. He was devastated by the death of his mother in 1903, when he was only 14 years old. Clarke was then apprenticed into his father's studio, and attended evening classes in the Metropolitan College of Art and Design. His "The Consecration of St Mel, Bishop of Longford, by St Patrick" won the gold medal for stained glass work in the 1910 Board of Education National Competition.