It’s a cold foggy Saturday and time for a lie-in after a week’s teaching. But I’ve just come in from a training session that started at 6.45am. What makes a teacher drag herself out of bed at such an unearthly hour? No, it wasn’t the London marathon; I’m training for a trek in Tibet that I’m undertaking on behalf of the charity Mencap. It goes without saying that you don’t have to be mad to teach, but it helps. It is this small streak of insanity that makes me want to swap the peace and serenity of a Year 1 classroom for the windswept, oxygen-depleted mountains of the Himalayas.

About 18 months ago, an article in our local newspaper asked for volunteers to raise funds for Mencap. I’ve always wanted to go to New York, but not to run a marathon. I admire camels from afar but, after a brief encounter with this stately beast in Lanzarote, I don’t want to cross a desert on one. So my final choices were narrowed down to a 400km cycle ride in China or a 160km trek in Tibet. I like to think of myself as being reasonably numerate, so after a quick comparison of the distances, my challenge chose itself, particularly as I wanted to return fit enough to go straight into the classroom. The first major challenge was not getting a place on the trek, but getting two weeks’ unpaid leave during term time. However, my head, Erica Barker, and the governors agreed to my applying and I have had their support ever since.

And then, as so often happens in my life, I sat down to read all about it. The literature assured me that I only had to be relatively fit - relative to what, I thought? As PE co-ordinator I felt that I matched this description. he trek starts with 90 other entrants outside Kathmandu this Sunday, moving into Tibet, where we will walk up to the Shung-La Pass (about 5,050m above sea level) over seven days - a journey of 160km. I walk my dog a few kilometres each week so was confident I could do this. Until, that is, I went to London to find out more.

The first point that registered was the organiser’s excessive use of the word “uphill”. He barely managed to complete a sentence without it. Another favourite phrase was “lack of oxygen”. I am at an age when I need all the oxygen I can get so I didn’t find this information very comforting.

My easy stroll was beginning to turn into a serious challenge. At this point I wished I had read the small print before I sent in my application. Three months and many miles later, I also wish I had tried walking 16km at a stretch regularly, just to see how it felt. But the truth is, I am enjoying the walking and trips to the gym, although the foot and mouth crisis has curtailed my country and hill-walking.

The most important aspect of the trek, though, is to raise as much money as I can. When I first started to fundraise I approached local schools to hold a non-uniform day, or something similar. I received many positive responses, from which I have raised a substantial proportion of my pound;2,500 minimum target. I have had the chance to visit the schools to talk about the charity and the trip. One thing I have learned - apart from the fact that I’m not as fit as I liked to think - is that schools do a tremendous amount of fundraising for a wide range of charities. This really has encouraged me.

Karen Hardmeier teaches at Shotley community primary school, Suffolk.email: hardmeier@aol.com