The Preston School District will be changing to a four-day school schedule beginning next year. Members of the school board voted unanimously Wednesday night to make the change as one of the ways to deal with major budget problems. Earlier this week patrons of the district went to the polls and voted to approve a $250,000 supplemental levy on a 59 percent to 41 percent vote. Passage of the levy means property taxes will increase about $61 on a $100,000 taxable value.