Minnesota's older teenagers are supposed to be hitting the books, at least if they want to legally ride a snowmobile. A new law requires all teenagers to pass a safety course before operating a snowmobile on public land. But few of the older teens have signed up for training, and public safety officials fear many are unaware of the law, or intend to ignore it. Minnesota Public Radio's Bob Kelleher reports ..... The snowmobile season got off to a slow start this winter.... SFX: (vroom - ratta tat ratta tatta tatta - vroom) For two days in November at the annual Snowcross races just outside Duluth