Issy Bennett is still wearing the same baggy jumper she wore when she was eight months’ pregnant, over a year ago. It used to belong to her 6ft 4in husband, but she has adopted it as a staple part of her wardrobe at Bromley High in Kent. Issy does not own a skirt and the last time she wore a dress was at her wedding 18 months ago. Today, however, the 38-year-old is almost unrecognisable in a lilac dress and knee-high black boots. “I can’t believe it’s me,” she beams into the mirror. “I don’t scrub up too badly, do I?”

The transformation comes courtesy of The TES Magazine’s Looking Good competition, which set out to find Britain’s worst-dressed teachers. Issy Bennett and Craig Cairns, a primary teacher, beat hundreds of hopefuls to steal the crown and were declared the winnerslosers by the fashionable TES editorial team.

Each received pound;500 to splash out on clothes at John Lewis, plus two fashion advisers to help them spend it. Issy, who owns just one lipstick which she never uses, had her make-up done by Bobbi Brown artists, while Craig was bronzed, glossed and concealed using Clinique’s male make-up range. They also had their hair cut and styled courtesy of Toni Guy in Soho, London.

“It’s been absolutely fantastic,” says Craig. People often think the newly-qualified teacher is older than his 25 years - something he attributes to his “timeless” uniform of tracksuit bottoms and dangerously putrid trainers. “My girlfriend usually shaves my hair for me and I buy most of my clothes at the Oxfam shop in York, so this is all a bit of a shock to the system.”

Now with a trendy Beckham-esque haircut more befitting his age and decked out in a smart brown jacket and spring-green top, he’s ready to re-enter New Earswick Primary in York with his head held high. “I didn’t tell the kids about the competition, so they were not quite sure when they saw me in school with a jacket on, but I don’t think they noticed a dramatic change.”

The same cannot be said of Craig’s colleagues, who were shocked to see him looking so smart. As he is the only male teacher at the school, they also welcome a more well-groomed specimen in the staffroom. Craig usually only dresses up for parents’ evenings, although he was put off after being told his shirt was tucked into his pants.

Carole Farrar, his headteacher, has gently suggested he abandon his scruffy ways - or at least his hoodie - in school. When he did not, she nominated him for the competition. “Craig’s wardrobe was definitely in need of updating,” she says. “He did a nice line in mix and match: woolly jumpers teamed with tracksuit bottoms or cottonlinen-mix drawstring trousers. His most unexpected outfit was a salwar kameez (loose baggy trousers and long shirt) from Pakistan.”

She is bowled over by the extent of Craig’s transformation. “I can’t believe the difference. It feels like I’ve got a new member of staff. All the other teachers need a makeover now just to keep up with him.”

Kay Ross, the John Lewis fashion adviser who dressed Craig, is despondent about the way teachers normally dress. “The typical teacher is like a perpetual student,” she sighs. “They’ve gone through the educational system themselves and then they don’t really raise the stakes when they become teachers. They want to make more effort but they don’t necessarily know how.”

Her remit with Craig was to make him look younger, “more edgy”, and drag him out of his comfort zone. She dressed him in autumnal colours to match his olive complexion and went for a smart-casual look which would work well in the classroom and for special occasions. Craig insists, however, that ties should be avoided at all costs - they only get in the way and inevitably end up in a pot of glue. Other than that, the only problem encountered was an issue with sleeve lengths, which rarely seem long enough for tall men like Craig.

Issy, meanwhile, was learning a few home truths from Amanda Slader, her fashion adviser, who said the teacher was not overweight but “column shaped” - straight and narrow with a good bust. “Hidden underneath all these big baggy clothes is an absolutely beautiful body crying out for more fitted clothes,” Amanda says. “She is aware of her stomach so we’ve used an undervest that fits the bust line and gives some control over the tummy.

We’ve also used layering and got her to show off her fabulous legs.”

Having been more comfortable in men’s leisurewear, Issy is now the proud owner of two skirts, a dress, cropped jeans and lots of V-neck tops. “It’s a million miles from her Nike sweatshirt,” says Amanda, stepping back to admire her work.

Although Issy is a PE teacher and wears sportswear during the day, she is now going to dress up for school events and going out. “I just like to be comfortable so have always worn men’s polo shirts or any clothes that are not too fitted,” she says.

“Pupils can be very perceptive and critical if you try to be too fashionable. But I think today might be a bit of a turning point for me.

After all the compliments I’ve received, I don’t really have a reason to hide behind my clothes. I’m going to start showing off my figure a bit more.”

It is a relief for Wayne, her husband, who may finally get his jumpers back. “When I sashayed downstairs all dressed up,” says Issy, “he just said, ‘Blimey, you look all right actually’. That’s quite a statement for him. I think he expected me in smart trousers and a top so he was quite taken aback to see me in a dress.

“I can’t wait for the next night out so I can get all dressed up, hold my head up high and strut about in all my new clothes.”

Top tips for men

Relatively plain shirts, always tucked in.

A pair of cords or chinos instead of jeans.

The right length trousers: without shoes, they should be touching the floor.

No trainers.

Keep a jacket at school for smarter occasions.

Take fashion tips from: Dylan Jones, Ewan McGregor, Rupert Everett and Ben Shephard.

Top tips for women

Properly fitted clothes.

Soft colours as opposed to bright patterns, flamboyant designs, or too much floral.

Skirts on the knee or below.

If large-busted, wear “modest” v-neck tops, not polo-neck jumpers.

If wearing soft colours, be bolder with accessories.

Take fashion tips from: Emma Thompson, Jennifer Aniston, Dame Helen Mirren and Erin O’Connor.