The college is based in and around the 12th-century St Donat's Castle in the Vale of Glamorgan, which earlier this century was used by US media tycoon Randolph Hearst. Terraced gardens lead down to the sea. In the medieval coachhouse, some students sing while others put the finishing touches to stage costumes. Others are having lunch in the timber-beamed refectory. In the library, students sit on stone windowsills, next to books on African history, Norwegian and Asian literature.
But it is not just the setting that attracts students. Atlantic is the British college that pioneered the International Baccalaureate diploma. While the debate over post-16 education goes on, as far as principal Colin Jenkins is concerned, the case is proven. "We've been doing it for 26 years. We'd be damned foolish if we were still doing something people didn't want," he says.
There are 27,000 students at the United World Colleges of Atlantic. In Wales, there are 350 from 70 countries - 85 per cent on scholarships. "Many are from the developing world, from refugee camps or inner cities," says Mr Jenkins. "They are not all part of the jet set. Admission is on merit and not on ability to pay."
He gets angry about the charge of elitism levelled at the International Baccalaureate. "The IB is not one jot more elite than A-levels. Yes, it's expensive, because it's an international qualification. But people start at the cost end rather than looking at the kind of education we want people to have."
That education - in line with the vision of college founder Kurt Hahn - is broad-based, highly academic and international. "The college makes the world seem a smaller place," says a student from Albania. Intellectual ability is combined with a "think globally, act locally" outlook: last year students did 54,000 hours of community service.
The major difference in curriculum between the WelshBac and IB is the latter's lack of vocational studies. The six subject groups are: individuals and societies, experimental sciences, technology, maths, arts and music, and subject choice. There is a theory of knowledge element, and a long essay.
On graduating, the majority go on to college or university - the IB is accepted by 650 universities in 80 countries. Last year Atlantic students gained five full Harvard scholarships.
Mr Jenkins believes that continuing the A-levels programme is a mistake. "Everyone agrees they are too narrow. Universities complain that students can't write. Employers complain that young people can't do simple maths - or even turn up for work."
Sir Ron Dearing's alternative of a national diploma is elitist and patchy, and his idea of the AS with a 17-plus examination is misguided, Mr Jenkins argues.
"The WelshBac may need refining. But Peter Hain (the Welsh Office minister for education) said basically the argument is won. We now have to find support from English universities. We're persevering."