From lowest socioeconomic status to highest, the categories are A, B, CD, DE, FG, GH, I and J.
Union avoided problems by converting Jefferson Elementary into a sixth-grade only school called Central 6 and bused all children in the district in 6th grade to Jefferson Elementary School.
It was later renamed Central 5 housing all fifth-grade students because the two junior highs, Burnet and Kawameeh, became middle schools and took on sixth grade students.
As a Type II school district, the board's trustees are elected directly by voters to serve three-year terms of office on a staggered basis, with three seats up for election each year held (since 2012) as part of the November general election.
The board appoints a superintendent to oversee the district's day-to-day operations and a business administrator to supervise the business functions of the district.