After leaving school, Allen obtained a scholarship at the Royal School of Woodcarving in 1880. Following a period spent in a successful carving workshop, and a brief period as a solicitor’s clerk he returned to education and entered the Royal College of Art in 1884. There he came under the influence of its Director, Thomas Armstrong, a disciple of William Morris and the Arts and Crafts movement. This was to have a profound effect on Allen's artistic development, and remained the predominant stylistic influence throughout his long working life. He also won many prizes, including, in 1888, a silver medal and a travelling scholarship of £50 which enabled him to take the first of many trips to the Continent.
Allen returned from Milan in May 1889, and later the same year was appointed as Art Master at Farnham School of Art. He was later promoted to the post of Director in recognition of his talents, and also put in overall charge of the teaching of art in the local primary and secondary schools.