Elk River is the state's second school district to approve a four-day week for its students. The Osseo school board decided last week to institute a shortened week next year. Officials in both districts say the move will allow schools to save on transportation and energy costs. A handful of smaller districts around the country are currently using the four-day week schedule. The tiny Calhan district in central Colorado shortened its week in 1980. District officials estimate the move cut costs by about 2 percent. District Superentendent Bob Selle (Sel-lee) says he was initially skeptical the savings were worth it. But he says four different studies show the four-day week has no affect on achievement: