Has the Arlington school district's at-large school board grown obsolete and unrepresentative?It's a question worth asking, as more nearby districts trend toward a single-member-district format.The idea hasn't gained traction in Arlington so far, but it's worth revisiting.The Grand Prairie district is looking into single-member districts at the suggestion of a board member, the Dallas Morning News reported Thursday. (dallasne.ws/X1lbjj) The district's 27,000-student population is 63 percent Hispanic, 18 percent black and 4 percent Asian. The seven-member board is all-male and all-white.The 34,000-student Irving district -- which is 71 percent Hispanic, 12 percent black and has an all-white board -- last year switched to five single-member districts with two at-large positions.With two Hispanics, Arlington's seven-member board is more ethnically mixed. But the lack of geographic diversity is stark: three trustees live in the 76016 ZIP code, not far from Lake Arlington on the west side; three live in North Arlington (two near Randol Mill Park and another north of Rangers Ballpark); and one lives near the University of Texas at Arlington campus. None live south of Interstate 20. None is close to southeast Arlington, which has perhaps the city's largest concentration of lower-income residents.The Arlington district's 64,500-student population is 43 percent Hispanic, 24 percent black and 7 percent Asian.Neither race, ethnicity nor home base determines whether trustees are able public stewards on behalf of students and taxpayers. But board members are less likely to know what's happening in areas of town they don't live in. Residents are less likely to feel connected to representatives they don't see at their churches, stores and neighborhood events.The arguments over single-member districts cut both ways.Having board members who are beholden to a constituency from a specific area ensures that neighborhood concerns don't get ignored. But trustees must take care not to lose sight of their obligation to the district as a whole.For now, any structural changes would require approval from the Justice Department or a federal court. Even if that weren't the case, a switch almost certainly would involve struggles involving boundary lines and competing interests.More racial, ethnic, geographic or economic diversity on school boards doesn't guarantee better schools, but it can improve representation by bringing a broader range of voices to the discussion about how to improve education for all students.