The Jefferson County Board of Education has selected a new student assignment plan for the school district.The board unanimously chose what's called the "contiguous boundary" plan, which places elementary schools in six regional clusters, each containing 12 to 15 schools from which parents can choose.The district's previous diversity plan was struck down as unconstitutional last year by the U.S. Supreme Court because it was based solely on a student's race.It required that each school have at least 15 percent and no more than 50 percent African-American enrollment.The new plan broadens the requirement to include factors such as household income and educational attainment of adults in a particular region.JCPS Superintendent Dr. Sheldon Berman urged the board to adopt the proposal."We've come to a plan that by no means is perfect, there is no perfect plan, but is the best we could do to balance the various factors that we had to balance," he said.The plan chosen by the board was one of two under consideration. The cluster concept does not include middle and high schools, which still must adhere to the new 15-50 requirement.The new plan will get some fine-tuning at a special board meeting later this month.