For years, people have known that something's wrong with the Chinese obsession with overseas travel-cum-study courses for young students.

While parents lament the ever-increasing costs of sending their children to study in developed countries for a couple of weeks, educators doubt the value of a course that offers more whirlwind sightseeing than opportunities to learn in a foreign country. And social critics detest the "immersion" tours as a rich children's hobby and a symptom of a widening social divide.

But probably it's school principals who really know how bad the phenomenon has become because they have worked with tourism companies, including those that are not qualified to run summer or winter camps abroad, to turn the courses into a dodgy multi-billion-dollar business.