IT'S not often a teacher can leave a class of Year 10s speechless.

But that's exactly what happened when Philippa Aldridge revealed she'd 'lost' one of her pupils.

The science teacher from Benson showed her class a picture of herself before she shed a whopping 7st 9lb.

"They were stunned," said 29-year-old Miss Aldridge. "They just looked at me in disbelief.

"Then one of them said: 'Mam, that means you lost Nancy! And it was true - I'd lost the equivalent weight of one of their classmates."

While she laughs at how her pupils at Gillotts School, Henley, reacted to her 'old' self, Miss Aldridge admitted she had found it hard trying to persuade children to be healthy when she weighed 17st and was a size 24.

"As a biology teacher, I had to teach pupils a bit about a healthy lifestyle and sensible eating. I felt such a fraud when the way I looked was such a bad role model for them."

She said her problems started at a young age.

"We had good hearty home cooking, but I ate big portions and just piled on the pounds.

"I weighed around 15st when I finished school. I did lose a couple of stones in my gap year while rushing about stacking shelves in a supermarket job. But I put it all back on again, and more, when I went to university.

"I was a typical student, knocking back the beers and working into the small hours drinking mugs of black coffee to keep me awake."

By the time she finished her studies, she'd shot back up to 15st and was a size 20.

But she said it didn't hit home quite how large she'd got until she injured her back moving house in 2001.

"I was off work for seven weeks and I remember the GP saying it would take longer to heal as I had to carry all my extra weight around. I was in terrible pain all the time."

Miss Aldridge joined her nearest Rosemary Conley Diet and Fitness Class in January 2002, and soon started to shed the pounds. In January last year, when she moved back to Oxfordshire after time away teaching, she weighed 13st 3lb.

"Although I was still big, none of the pupils ever made horrible remarks about me," she said.

"By that time, I'd also discovered I got a buzz out of doing aerobics and had really got into exercising, so the weight was coming off all the time.

"I really loved doing the sessions and the feeling it gave me afterwards, so I took a distance-training course and I'm now teaching aerobics classes for Rosemary Conley."

She added: "I reached 9st 6lb this year and I feel fantastic. I've now got a healthy glow, better skin and I sleep much better than when I was overweight."

Miss Aldridge's boyfriend, Tyrone Guthrie, 27, a plant operative at Grundons, Ewelme, is impressed. She said: "We started going out when I was 14st, so he knew me when I was big, but he says I now deal with stress much better and am much more confident."