He recalled the anxiety of his first day, aged 12, newly-arrived from Somerset, wearing the hideous brown uniform that was then the order of the day at Abersychan comprehensive, near Pontypool, Torfaen.
He also remembers the furious red pen of his English teacher, Ma Bart, slashing through his homework. Yet, despite her uncompromising attitude to marking, the classroom dragon inadvertently encouraged him to write.
"She ran an Eisteddfod poetry prize, which I entered aged 15. The theme was spring, but I based my poem on a Beatles' lyric. With the arrogance of youth, I was convinced I would win."
He had no chance, having failed to stick to the brief. But the joy of self-expression through verse remained.
A lifelong Bristol City fan, and the club's official poet laureate, Mr Calway used football metaphors and his book of football poems, Sheer Paltry, to pass on the power of poetry to a group of 30 Year 8 schoolboys who attended his workshop at the school last week.
"Football chants echo the call-and-response form of poetry that harks back to Greek theatre, and is also found in African tribal chants and blues music," he said.
Now based in Hunstanton, in Norfolk, where he is head of English at Smithdon high school, Mr Calway has just published his seventh poetry book, Exile in His Own Country.
The title refers to his own experiences of being an English boy entering the Welsh valleys, and conversely being a Welshman in Norfolk. This duality was part of the appeal when Abersychan headteacher, Mike Conway, invited him back to perform.
"It's important for the pupils to experience someone coming in from the outside, but Gareth, ironically, is also from their own community," said Mr Conway.
Mr Calway's work seemed to strike a chord with the Abersychan lads, who are taught English separately from girls at the mixed comprehensive, following a pilot scheme run with Bath university.
"I always thought poetry was boring before, and didn't go with football, but this is fun," said Liam Cowels, aged 13.
Like Ma Bart before him, Gareth Calway aims to organise a poetry competition at the school. But entrants will not be penalised for failing to write about spring.