LA POINTE, Wis.  From a distance, the large red aluminum contraption parked on the frozen shore of Lake Superior here looks like a small houseboat perched on skis. Up closer, as schoolchildren pile in with their backpacks and iPods, it becomes clear that the mystery vehicle, with two large fans on the back, is something else entirely.

For residents of this remote village on an ice-locked island off the tip of mainland Wisconsin, the gliding boatmobile, known here as a windsled, is a kind of school bus.

That’s right: in one of the more unorthodox modes of student travel anywhere in the country, the children of La Pointe, on Madeline Island (full-time population 250, triple that in the summer), actually windsled to class several weeks out of every year. It is the transportation a school district needs when students are separated from class by more than two miles of jigsaw ice blocks coming together to form something that approximates a floating road of shallow depth across a bay.

Everyone here knows the windsled as a homegrown solution to a tricky set of circumstances: Sometimes Lake Superior  the largest, coldest and deepest of the Great Lakes  is too chunky with ice for a ferry but not quite solid enough to make an ice bridge between La Pointe and the mainland town of Bayfield, the location of the upper school.