Imagine a lesson lasting 18 months. Most adults find it difficult to engage a teenager's interest for 45 minutes, but Outlook Expeditions, which offers adventure eco-tourism to young people, provides an experience that lasts a year and a half. That's how long it takes from the initial planning stage to fundraising and the trip itself. The promise of scaling mountains and coming face-to-face with exotic wildlife amounts to a rite of passage whose lifelong lessons simply aren't possible in school.
This year Zambia has been added to the firm's destinations. It already covers Bolivia, Patagonia and Peru, as well as Borneo in Indonesia, Kenya and Tanzania.
For teacher Margaret Howells of Aberaeron comprehensive school in Ceredigion taking a group of 10 pupils trekking through the Bolivian Andes last summer promised adventures too great to turn down.
"It was a complete culture shock," she explains. "Everything was so different: smells, tastes and views. It was brilliant - better than going to France or Europe. The company takes you to an isolated community, something you'd never do as a tourist."
The South Wales group spent a month in Bolivia, the country at the highest altitude in South America. A custom-made itinerary included hiking in the Noel Kempf National Park, a biodiverse virgin rainforest which only a few dozen people are given permission to enter each year.
Before the trek, Ms Howells' party stayed in the remote village of La Florida, painting the local school. Then it was off to the highest navigable lake in the world, Lake Titicaca, before heading to the final stop in Bolivia's capital city, La Paz.
Other expeditions run by Outlook last year included one to Patagonia, which also provided the opportunity for students to experience a typical trip: trekking through extreme natural features, interaction with indigenous communities, charitable deeds, wildlife sighting and a stay in a capital city, in this case Buenos Aires in Argentina.
The month-long trip, though, is just the final stage in the journey.
Preparation starts with three group development days spread out over the 14 to 18-month period. On the first day, the students work on team-building tasks and discuss fundraising strategies.
In the second session, the group designs its itinerary from a selection of activities on offer for each country. The final step is to introduce the expedition leader - someone selected in a rigorous process that can take up to year - and familiarising the teenagers with their trekking equipment.
The class then goes on a mini expedition in Snowdonia in Wales, where Outlook is based.
Once the students have returned from their big overseas trip, they have one last refresher day that allows them to review the skills learned throughout the year.
Those who are concerned about security - both personal and political - can be reassured by the company's thorough controls.
All destinations and activities undergo an exhaustive risk assessment and all are continually monitored through the Foreign and Commonwealth Office.
The groups are also supplied with global positioning systems (GPS) and satellite phones that connect them to a 24-hour safety operations room which can dispatch emergency services within minutes.
"It's all about having a life-changing experience," says Emma Youde, Outlook's expeditions manager. "It's quite an incredible opportunity. I can't help thinking, 'Gosh, I wish people were doing this when I was 18 years old.' "