"I don't feel the need to win any more awards," she said after the ceremony at the Groucho Club in London's Soho.
Ms Clanchy, a regular contributor to the TES, found the build-up to the announcement stressful. "We had to be kept in suspense til the last moment. I thought Alice Oswald would win. She's very good." In fact, Alice Oswald came third.
The Forward poetry prizes, the most valuable annual awards in the UK, were founded by William Sieghart, chairman of Forward Publishing and founder of National Poetry Day.
Ms Clanchy's first success came in 1994 when she won the Eric Gregory Award from the Society of Authors for writers under 30, only 18 months after she started writing. A boyfriend had told her to "stop whinging, go home and write a poem that is 63 words long".
Ms Clanchy was born in Glasgow in 1965 and educated in Edinburgh and Oxford. She taught English for six years before going part time two years ago at Havering Sixth Form College in Romford, Essex, where she is now writer in residence.
She was inspired by a course run by the Arvon Foundation, a charity devoted to promoting creative writing, and began to encourage her students to write poetry. She makes verse accessible by using comprehensible language and contemporary references to get across the idea of metaphor and sound forms.
She believes that the precision of poetry, the drafting and redrafting, is invaluable to A-level language students. "For sheer clarity of writing and for learning the real rules of punctuation, I think poetry writing would be handier on a business English course than any number of model letters," she wrote in The TES after winning her last award.
Havering College was very generous and supportive about her work and award, she said. Students joined in the celebrations. "It's good for them to know a poet who is a woman and not dead."
Her book Slattern, published by Chatto and Windus (Pounds 6.95) is widely used by the English department for GCSE and A-level coursework. She encourages students to criticise her work. "They learn that the work is more important than me - I'm a non-sacred object which is very useful in education. I still write about them."
And she thinks it's good to be a teacher as well as a poet. "Poets can be demandingly anti-Establishment. I understand the constraints of the timetable. "