The experience may have prepared her for her new role as Britain's first full-time schools liaison officer for stammerers, but it is a memory which pains her to this day, 30 years on.
"The headteacher came into my sixth-form classroom and told us to speak to her then and there if we were interested in applying to Oxbridge," said Cherry. "I was quite academic, and I was interested.
"I can remember standing up, walking towards her and composing myself to speak - but just knowing that I couldn't face the struggle and embarrassment of getting the words out. So I sat down again. I'm not saying I would have got in to Oxford, but I lost the chance of applying and finding out."
Mrs Hughes, fresh to her role as the British Stammering Association's schools liaison officer, is determined to reduce similar problems for the 5 per cent of schoolchildren who stammer.
The Stammering Association, which has 1,500 members, says help given to stammerers at school can change the whole course of their lives. At present, teachers lack knowledge of how to tackle the problem, the association says.
As a result, Mrs Hughes, formerly deputy head of Woodford Lodge High School in Winsford, Cheshire, has just begun a year's pilot scheme of in-service teacher training in the North-west which will then be extended nationwide. The two-year Helping Stammering Pupils Programme has received funding from both Comic Relief and the Lloyds TSB Foundation.
"Stammering is a bit of an unknown quantity for teachers," said Mrs Hughes. "It can be difficult to identify because stammerers are often reclusive and don't talk."
She says the answer is for teachers to be given more information, with leaflets and videos available from the association. Simple procedures can make sufferers feel more comfortable about speaking in class, and she plans to help schools co-operate with speech and language therapists.
"It's absolutely no good if a child has support at a speech clinic, but then goes into school and no one responds to their needs," she said.
And the good news is that most stammerers can conquer their difficulty in expressing themselves: although one in 20 children is affected, only one in 100 continues stammering into adulthood.
But Mrs Hughes received no help at all from the teachers at her Liverpool grammar school in the 1960s.
"My stammer was not considered worthy of discussion," she said. "If I did try to speak, it was a case of 'Do hurry up!' or 'Can't you try a little bit harder?' It blighted my life, and I used to go home and cry."
The inconsiderate treatment she received compounded her anxieties - and it was only when she went to study at Leeds University that her long years of public silence ended.
"One of my lecturers was blind, and he had a positive attitude to disability, " said Mrs Hughes. "He said, 'You're an academic - read about stammering'. "
She soon discovered that stammering was already recognised as a medical condition in America and Australia, and set about finding ways of controlling it. She worked out which situations caused her the most difficulties, and through breathing techniques and strategies of detachment - tackling those problematical situations by pretending she was playing a role - within two years her stammer had gone for good.
If her scheme is successful, she believes many thousands of young stammerers could have resolved their wrestle with words long before they leave school.
"The most important thing with a stammering child is to recognise their problem and give them time, ensuring they can talk," said Mrs Hughes. "All it needs from teachers is prior planning."
STAMMERING; A ROUGH GUIDE FOR TEACHERS
* Slow down your own rate of talking so children know there is plenty of time.
* When asking a question of a stammering child, give alternatives: "Did it happen in class - or in the playground?"
* Comments on the emotions exacerbating a stammer - "I can see you're cross" - can be helpful. Comments on specific words or sounds often aren't.
* Encourage stammerers to talk about their personal interests: they are likely to feel more confident.
* Remain calm: with a little thought you will be able to help the stammerer.
A Teachers' Video Pack is available from the British Stammering Association for Pounds 11.95, including postage and packaging, from BSA,15 Old Ford Road, London E2 9PJ.Tel: 0181 983 1003