Gatwick, a Friday in autumn, 8am. Somewhere about this airport are 562 teenage students and 69 teachers and supporting adults from 25 schools, because we are going to Istanbul for the day. We are disoriented but full of anticipation. There are teenagers in twos and threes, sometimes an obvious 10 with a teacher, but which are ours? Many have travelled overnight and look sleepy.

After Istanbul we are going to Ephesus, Cairo, the Pyramids, Jerusalem, Bethlehem, the Dead Sea, Knossos and Heraklion, from where we shall fly home the next Friday. The distances will be covered in the Romanian-built, 11,563-tonne cruise ship Aegean I, with her bulbous bow and Denny Brown stabilisers. We are understandably excited. Some inspection party adults are also here, to assess this trip organised by Voyages of Discovery.

Already the level of organisation is notable: we are well briefed, we have the right documents, we know exactly what to expect. Throughout the week nothing happens that we are not prepared for, which is just as well, because when we get on to 13 coaches for a visit it looks like a troop movement and we cause traffic jams throughout the Middle East. One of the coaches carries only a ship’s nurse and the doctor and is spare in case of breakdown or if someone has to return to the boat - because of our Greek crew there is no coach number 13.

The Voyages of Discovery staff have to get 634 people from plane to boat. They do it skilfully and we clamber aboard in our house divisions. It is grey and raining but the students are keen to explore. We find our cabins, which are comfortable and unassuming, and we unpack, and students start to be called for supper. Everyone dresses up like mad. Tomorrow, the Blue Mosque, and our first sail. What an extraordinary adventure! Swallows and Amazons flickers into mind.

The topmost of the eight passenger decks is the Belvedere Lounge, soon a popular rendezvous for grown-ups. It has the best view, festoon curtains, little lamps on low tables, and we go there after dinner to do quizzes and take liquid refreshment. Cruise staff member Sue Dennis tells the story of school cruises.

Educational cruising was introduced in 1932 when a Government troopship carried a group of Scottish schoolboys for a two-week voyage to Scandinavia. The objective was probably the same then as now: adventure, self-discovery, world sites, broadening the mind, and a shot at carefully protected independence.

The case for this kind of trip is that of self-determination, big experience, larger perceptions. Practically, the teachers note how much easier it is to locate their groups on a boat than in a hotel, also that the shore visits are well prepared. The cruise staff are led by David Baskott, who describes himself as the world’s only ship’s headmaster and believes the students go home “six months older”.

Saturday brings life-jacket drill in the rain. Our first trip, to the Blue Mosque of Suleiman the Magnificent and the Topkapi Palace, is drenched. The guides tell us about the Eastern Roman Empire and the Ottoman Empire and the Byzantine period, and about Istanbul straddling the continents of Europe and Asia, but we still have questions.

Why are the royal garments so broad? Why do the gold thrones look like double beds? Two boys consider the worth of the gold artefacts. “They could melt them down and feed the poor people,” says one. “But they’re works of art,” says the other. “They show how people lived ages ago.” “There are beggars outside now who haven’t got enough to eat,” says the first. Such exchange of values takes place throughout our week.

Many students are impressed by the mosaics on the ceilings of the Blue Mosque. “How could they dream it?” says a girl. Some practise folding themselves into the Muslim prayer position, others complain because they had to take their trainers off. Outside, street sellers rush at us with fistfuls of umbrellas shouting “Brella! Brella!” a cry taken up by the students for the rest of the week. It is their first experience of aggressive selling. “I found it disturbing,” says Leonie Stewart of Walton Girls’ School in Grantham, Lincolnshire.

And at last we sail. Sue Dennis says they pray for good weather during saltings but the students seem to find things to do anyway. They gossip in each other’s cabins, borrow clothes, play games, rent hairdriers, and hang out in the bars buying soft drinks with swipe cards which they recharge with Pounds 5 notes.

With luck, the Italian ship’s magician might teach you a trick. If not, he will pass the time of day and then hand you back your watch while you gasp at his cleverness. There are lectures in which we learn something of the history of the next stop and the ways of its inhabitants: whom to barter with, which hospitality to accept, which to avoid. They strike a nice balance between history, anecdote and practical tourist information.

The majority of the ship’s complement is girls, with the ratio to boys slightly worse than 3:2. Apparently this gender bias is usual on school cruises, nobody knows why. It is a nuisance on Blind Date evening (adults excluded) and at the disco, less so on Greek Night when their attention is focused on ships’ heart-throb and Neighbours clone Tom Bills, who comperes in traditional Greek costume.

David Baskott has been running cruises since 1979 and calls them, “the residential experience par excellence”. He says that for years afterwards, mention of one of the countries or sites will arouse a memory or stimulate an untold anecdote, and reports parents saying: “My kid has grown up in a week.” Staff member Anne-Marie Cretien went on her first cruise at 12, her second at 16. “I talked and talked about it. I took six rolls of film. A lot sinks in without you knowing.” And the benefit for students? “I think they go home amazed,” she says.

Actually, we are constantly amazed. We are amazed by Ephesus, not having imagined such a clear impression of life 2,000 years ago. The mosaics worry us. “You’d think they’d cover them,” say three of the girls. “Surely the rain will damage them?” On the steps of the Grand Theatre, teachers photograph their groups. Since most pupils wear the voluntary uniform of trainers and wide, blue, track-suit trousers with opening side seams, the pictures are oddly reminiscent of the end-of-term school photo.

Teachers say these trips improve personal relationships, and tell stories of greater friendliness and respect, and of being invited to listen to student gossip. However, few students can bring themselves to take up the offer of using teachers’ first names and those who do so drop it as soon as they get home. The experience, says Walton’s Kate Manley, “helps remind me why I like teaching - I get pleasure from seeing the girls enjoy it”. For English teacher Elaine Murphy of Saddleworth School, Oldham, this is the first big trip. She feels well supported. “Of course it’s work, but it doesn’t feel like it, ” she says.

Tuesday: Tutankhamun, and the pyramids. Reveille is 6am. We are woken by the reassuring Scots voice of cruise director David Burgess on the Tannoy and a ghastly song about an old bazaar in Cairo. We have many coach hours ahead but are stoical, perhaps with a precognition of the wonder of David Reynolds of Earls High School, Dudley, in the person of Lawrence of Arabia, galloping across the sand dunes on a camel behind an Arab in full regalia.

Most of the pupils enjoy their camel rides. “Fabulous,” say two boys from the north, “you think you’re going to fall off.” (Fortunately they do not know that riding camels gives you ulcerated boils on your backside.) On our way to the Sphinx a group of Middle Eastern schoolchildren greets us with a chorus of welcome but we are not sure how to respond.

The pyramids, for which no adequate adjective exists, mystify us as much as did the gold sarcophagi of king Tutankhamun. We stare, we are poured into gift shops, and then we spend hours in traffic jams contemplating our police outriders while Tom Bills maintains our good humour. We get back to the boat at l0pm to find that a market has been set up to sell us things while we queue to climb aboard. The trade in leather camels and camel switches is brisk.

Wednesday: Bethlehem, Jerusalem, the Dead Sea. It was suggested that students might sing carols at the birthplace of Christ and when they do we find ourselves extraordinarily moved. Our guide tells us carefully about the political situation, but loses our attention. We tend to prefer Bethlehem to Jerusalem. The students are again upset by the sight of beggars. “They hadn’t imagined this poverty,” says a teacher.

Most of us float in the Dead Sea, where the strangest sensation is created by not being able to put your legs down to walk out again, and some students say the Dead Sea is the best thing so far. Today, all the proper tourist ceremonies have been observed: petitions at the Wailing Wall, smearing the person with Dead Sea mud, purchasing Bethlehem knick-knacks.

On the last day we disembark from the Aegean I at Crete, where we visit Knossos and take in not very much. A few students try to bend their tired minds towards the Minoans and the ancient writing system of Linear B, but for most the effort is too great. We are touristed out, we are going home, we have run out of money and are ready to fly. For Zoe Smith and Suzannah Elliott of Walton Girls, their first word for the week is “Brilliant!” and their observations are clear and critical.

They have been especially impressed by their view of other lives, the street-sellers, the Jerusalem women begging with babies in their laps. “You take things for granted at home,” says Zoe. “I feel like a pilgrim. It’s opened my mind,” says Suzannah. “My parents wanted me to see how other people live, and I believe I have done. This has been the experience of a lifetime.” They were surprised by the seriousness of religious life and the extensive decoration of the churches.

They enjoyed the markets but were bothered by the attentions of the men, with whom they had to deal firmly. Here, they were as street-wise as the Midlands girls who after their Kusadasi day reported replying to invitations to, “come up and look at my workshop,” with “we just said, no thanks!” All the girls had two or three offers of marriage. Were they not tempted? “Ugh!” they squeal, then one says kindly, “The men can’t help it, they don’t know any different. ” Like many others on the trip, they kept diaries.

As good as six months’ experience, or more? As with school trips on one continent or three, the effect is hard to quantify with any precision. There is no denying it costs serious money, although given the quality of the experience and the immaculate and consistently good-humoured organisation, it is good value. For those who like boats, it seems a very good deal indeed.

PLAIN SAILING CRUISE DETAILS

Cruise information from Stephen Wheddon, Voyages of Discovery, Premiere House, Betts Way, Crawley, West Sussex, RHl O 2GB. Tel: O1293 433O3O.

Costs

* Cruises are booked up to two years ahead, and parents can often pay monthly. A week like this cost about Pounds 779 in 1997, going up to about Pounds 8OO in 1999. This price will then include flights, visits to museums and sites, lectures, ship facilities and travel to airports.

* Most students took Pounds 8O-Pounds 1OO pocket money. They had been encouraged to contribute to it themselves, and had saved gift money and done holiday jobs. It is needed for shopping on shore and in the bars.

* Discounts are available to accompanying adults who take on responsibilities or are on inspection visits.

Health and safety * Attendance at the introductory talks on board is compulsory.

* The ship has two nurses and a doctor, who are on call 24 hours a day. Nurses report some sea sickness and home sickness, the doctor speaks of “the usual range of GP problems”.

* In the event of serious illness, pupils are put ashore with a nurse. Medical help is free to students, and is covered by health insurance for adults.

* Once, a dramatic airlift from a ship back to the island of Cyprus saved a life. The student was suffering from meningitis. Six months later he was able to rejoin a cruise free of charge.

* Deck drill is practised as soon as students get on board.

* The ship conforms to international maritime law.

Study materials

* The Port Naut Guide and The Mediterranean Environment, given free to students, offer information about the countries visited, as well as navigation and ships. The accompanying workbook is pitched at GCSE study skills.