A wall of heat hits them as they step off the plane, signalling the start of an extraordinary adventure.
Cattle amble along dusty roads in baking heat, as the bus heads for the Gambian coast from the airport in Banjul, overtaking locals on donkeys and passing mango sellers by the roadside.
"It was one of those stereotypical African buses and I thought that was so cool," says Cerys Duguid, a 17-year-old redhead with fair skin and blue eyes. She remembers her first impressions vividly: "It was so different - the colours and smells, and it was so busy."
She had packed a sensible hat and suncream to protect her Celtic complexion from the searing heat of the African sun. But nothing could have prepared Cerys and her friends for the culture shock they were about to experience.
Eight pupils from Meldrum Academy in Aberdeenshire travelled last month to Kerewan in The Gambia to help build a vocational skills centre as part of their Duke of Edinburgh Award. They raised thousands of pounds to help fund their journey, helped by contributions from local businesses. They had little expertise in construction techniques.
Prior to setting off, Ian Jackson, the principal teacher of design and technology who accompanied them on this final adventure of their schooldays, had predicted it would be a steep learning curve, "getting stuck in and getting their hands dirty".
When they returned, he believed, they would be able to survive in any environment they went into, and would appreciate a lot more what they had at home, after sleeping on a mattress on the floor under a mosquito net for two weeks.
The pupils themselves anticipated that it would be "an experience of a lifetime", with the chance to make a difference to people who weren't as well off as themselves.
Louise Wilcox, 17, was a bit unsure what to expect, but really excited and "ready for a big shock" when she got there, because of the difference in cultures.
Louise and the others were working on a GAMSCOT (Gam-bia-Scotland) project, helping to build a network of skills centres where young Gambians get vocational training. This is a collaborative venture where Scots doing their Duke of Edinburgh Award work alongside young Gambians pursuing the equivalent award in their country.
One skills centre has already been built and provides education and training for 700 young Gambians aged between 14 and 25. A second is being built in a different part of the country, and that is what these Scottish teenagers were doing.
Two weeks in Gambia has certainly changed the way they look at life. It's only a matter of days since they came home to the sleepy Aberdeenshire villages where they grew up and they are looking wistful, like they have had a holi- day romance and didn't want to come home.
The happy smiles of their new Gambian friends have won their hearts. And they've been moved to see them enjoy life with such exuberance when they have so little material comfort and so much hardship.
"If I had my way, I'd still be there," says pupil Tim Reid, 17.
"I think we all would," says Joanna Ewenson, 17. "It's made me realise how important it is to travel - I just want to go everywhere," she says, reunited with four of her fellow travellers at her family home in Rothienorman.
As these five young Scots prepare to embark on the next stage of their education, they know how privileged their lives are compared with their new young friends.
Education in Gambia is extremely basic. They have to pay for their secondary education, so not every young Gambian receives it. The schools are overcrowded - there are not enough desks and chairs. Few schools have power and what power there is, is not regular. The schools are extremely basic. Textbooks are rarely available. Some of the teachers are qualified, but many are unqualified and not well paid - so the quality of education can vary.
"When we were there, one of the guys - his nephew died. He was at the beach with us and he just said: `I've got to go; my nephew's just died' - and he was only five years old. That was so sad, but it seems a part of everyday life for them," says Joanna.
She does not know how the boy died, but malaria is a major cause of death among children under five in this country.
As the group sits round the table reflecting on their experiences, there's a heatwave in Aberdeenshire. But it's mild compared with Gambia, where temperatures were heading towards 50C.
After spending the first four days acclimatising on the coast, they headed inland to Kerewan where their work began in intense heat. "Even in the evening it was probably still about 38 degrees," Joanna says.
The group worked alongside the contractors and young Gambians doing building work, digging, clearing rubble and building paths. They also took turns preparing the food and cooking - mostly spicy rice with meat.
"The building work was quite hard because of the heat. You were exhausted all the time," says 18-year-old Leah Brown, blonde with a striking patch of pink hair on one side. "But it was good banter at the same time, so it was lots of fun and there was always laughing going on."
At night, they slept in a school classroom, like a big shed, and were awakened every morning at 7.30 by 400 exuberant primary schoolchildren singing outside at assembly.
Aberdeenshire people have a natural reserve - but in The Gambia the teenagers got a large hello from everyone they met. People greeted them with hugs and their new friends held hands with them as they showed them round.
"The people we were with held our hands all the time. The first time it happened, I thought it was a bit awkward - but after that, you get used to it," says Cerys.
"Everyone shook your hand and asked you how you were, which was kind of odd," says Lucy Pape, 17, bewildered by this instant affection. "People don't normally greet you like that. But they all just said `Hi how are you?' - pretty much everybody," says Lucy, who starts studying to become a primary teacher after summer.
"Seeing a white person is rare for them, so you get stared at everywhere and all the kids start shouting the word for white person. So all the little kids are jumping up and down shouting `Toubab,' `Toubab'," she smiles.
There were none of the washing machines and tumble-dryers that are the soundtrack of family life back in Scotland. No fleet of family cars in the driveway. But living conditions were better than they expected, except for the toilet facilities. "They were pretty disgusting, just a hole in the ground," says Tim.
"There were around 800 children using them every day and there were cockroaches at night," says Cerys, shuddering.
The past fortnight has been an emotional roller-coaster for Tim, who claims, with disarming frankness, that he cried more than anyone. "The first time, which is pretty embarrassing, was when I called my mum," he confesses, as the girls smile sympathetically. "Then I cried when a guy's sister named a baby after me."
They all spent time at home with local families to learn more about daily life: "When I left and I gave them gifts, I was in tears for half an hour in the taxi back, and in the hotel," says Tim. "It was just so sad because they were all so happy, but they had so little and there were so many of them to share every- thing with."
The girls have noticed differences in the role of women and are fascinated by the African marriage customs: "They expect women to wash all their clothes and cook their meals, no matter what," says Lucy.
Joanne thinks some younger men take more of a share in household chores.
Lucy talks about one of the young men they met: "His dad had four wives with upwards of 20 or 30 kids."
Tim says: "You weren't considered a real man if you had only one wife."
"Two was a real man, more than that was even better," adds Lucy.
"I think four was the limit, though," says Joanna. "But it's assessed on whether they can provide for them, they're not allowed to have as many as they want."
As they head off to colleges and universities all over Scotland, they know how fortunate they are.
"It really shocked me that there is only one university and it's so expensive to go, and for people here, it's so normal to go to university," says Cerys. "Some of our counterparts really want to go, but they can't afford to."
The Scottish teenagers have barely had time to unpack, but they are planning return trips. Tim spent a week digging a hole for a septic tank at the new centre, and he and his friend Stewart are talking about going back in January.
Joanne says: "I'm just so glad I went - just to have that experience, it's quite a privilege."
GAMSCOT is an innovative collaboration developed by the participants of The President's International Award in The Gambia and the participants of The Duke of Edinburgh's Award in Scotland.
It offers practical work experience opportunities for the development of young people, development of a highly-skilled labour force, creation of high-quality goods and services and self-sustainable workplace for the benefit of The Gambia.
The President's International Award is now busy with the building work for the next skills training centre in the town of Kerewan in North Bank Region. Young people are playing a lead role in the development of the centre and, aided by their instructors, are helping with the construction work.
Pupils from Inverness Royal Academy and youngsters from Dumfries and Galloway have previously taken part in the project and welcomed guests from The Gambia. Inverness teachers have helped train teachers out there and more Scots teachers will follow.
Aberdeenshire's director of education, Bruce Robertson, is chairman of the Duke of Edinburgh's Award in Scotland and chairman of the GAMSCOT trust. He travelled out with the Meldrum Academy group. "I have been out before and it's a life-changing experience for these young people," he says.
"They see a different culture, they see a third world country, they see just how important education is for young Gambians - it is their passport."