Howson was one of the four sons of William Howson of Settle, author of An Illustrated Guide to the Curiosities of Craven (1850), and Headmaster of Penrith School; and the grandson of the Reverend J. Howson, second master of Giggleswick School. He was himself educated at Giggleswick, which he left in July 1879, and then at Merton College, Oxford. He matriculated at Oxford in 1879 and graduated BA (taking a First in the Final Honours School of Natural Science) in 1883 and MA in 1886.
All of his brothers attended Giggleswick School, Hubert Howson (born 1857) becoming a lawyer and settling in New York City, and Charles James Howson (born 1852) becoming a bank manager and Justice of the Peace at Chesterfield.
Howson's first position after leaving Oxford was as an assistant master at Newton College, in south Devon, from 1883 to 1886. He then moved to Uppingham School, where he remained for fourteen years, from 1886 until 1900, when he was appointed Headmaster of Gresham's School, Holt, continuing in post until his death in 1919.
When Howson arrived at Gresham's, a rather dusty ancient grammar school founded by Sir John Gresham, he found it in numbers much as it had been when established in 1555. In 1900, the school still occupied its original Holt town centre site and contained only forty Holt Scholars, plus seven boarders.
During his headmastership, Howson achieved a completely new set of school buildings on a new edge-of-town site, transforming the school and quadrupling its population. The first such new buildings, designed by the architect Sir John Simpson, were opened by Field Marshal Sir Evelyn Wood on 30 September 1903. These consisted of School House (renamed Howson's in 1919, after Howson's death) and the main classrooms building, including Big School. More boarding houses were acquired or built between 1905 and 1911. A new School Chapel was completed in 1916, during the Great War, during which one hundred Old Greshamians were killed.
He died suddenly on 7 January 1919. His Executors were Charles James Howson and James Ronald Eccles. The Times said of him "Under him the school made rapid progress, especially in science teaching", and "He has been called away, as he would have wished, while in the faithful discharge of his duty. His death has left a gap which it will be well-nigh impossible to fill."
J. H. Simpson later wrote of Howson's achievements at Gresham's:
He went there in 1900, when it was a little-known grammar school in a remote corner of Norfolk, and in the remaining nineteen years of his life he made it known throughout England for its bold and original methods.
A new school library was built in memory of Howson and opened by Field Marshal Lord Milne in June 1931. On 31 January 1932, a bronze bust of Howson by Kathleen Scott was unveiled in the library by Howson's successor J. R. Eccles.
Howson's publications include his Sermons by a Lay Headmaster, Preached at Gresham's School, 1900-1918 (Longmans, Green and Co., 1920).
- Howson, William at comcast.net, accessed 22 May 2008
- Giggleswick School Register, p. 58
- Benson, S. G. G., and Martin Crossley Evans, I Will Plant Me a Tree: an Illustrated History of Gresham's School (James & James, London, 2002) ISBN 0-907383-92-0
- HOWSON, G. W. S. Head Master, Gresham's School, Holt, Norfolk, since 1900 in Who Was Who 1916–1928 (A & C Black, London, 1992 reprint, ISBN 0-7136-3143-0, and HOWSON, G. W. S. in Who Was Who 1897-2007 online (2008) retrieved 22 May 2008 from HOWSON, G. W. S.
- Giggleswick School Register, January 1872, p. 66
- Lidell, Charles Lawrence Scruton, and A.B. Douglas, The History and Register of Gresham's School, 1555-1954 (Ipswich, 1955)
- When Heroes Die by Sue Smart (Breedon Books, 2001) ISBN 1-85983-256-3
- Auden: The lost poems in The Independent dated 5 September 2007 online at independent.co.uk (accessed 22 May 2008)
- Benson, Steve, I Will Plant Me a Tree (2002) p. 25
- "No. 31391". The London Gazette. 6 June 1919. p. 7355.
- Mr G. W. S. Howson in The Times, Thursday, 9 January 1919 (Issue 41993), p. 9, col. C
- A Notable Headmaster. Tribute To The Late Mr. Howson in The Times, Friday, 10 Jan 1919 (Issue 41994) pg. 11, col B
- J. H. Simpson, Schoolmaster's Harvest (London: Faber and Faber, 1954), p. 79
- The Times, Friday, 26 June 1931; pg. 8; Issue 45859; col F
- "Howson Of Holt" Bust Unveiled at Gresham's School in The Times, Wednesday, 3 February 1932; pg. 9; Issue 46047; col B
- Howson, George William Saul, Sermons by a Lay Headmaster, Preached at Gresham's School, 1900-1918 (Longmans, Green and co., 1920) online at books.google.com, accessed 24 November 2008
- Simpson, James Herbert, Howson of Holt: a study in school life. 93 pp. (Sidgwick & Jackson, 1925; Cambridge Occupational Analysts Ltd., new illustrated edition, 2010, ISBN 978-1-906711-09-2)
- Eccles, J. R., One Hundred Terms at Gresham's School (1934)