KANSAS CITY, Mo. — Like so many other public school parents, Reshonda Sanders felt confused on Thursday as she tried to comprehend why nearly half of the schools here, including her own alma mater, are to close for good at the end of the year. As the mother of two high school students, she was well aware of the district’s struggles.

“But even so, I thought, Could they be serious? Close almost 30 schools, all at once?” said Ms. Sanders, 34. “That’s devastating for us. How did it get to be this bad? What were they doing for years and years so that something like this happens just like overnight?”

In her bafflement, Ms. Sanders is not alone. In the wake of the Kansas City school board’s decision to shutter 28 of its 61 schools, many people were left scratching their heads. While school closings as a result of demographic change and tight budgets are commonplace across the country, rarely does a system lose half of itself in one sweep.

The sudden move suggests a depth of dysfunction here that is rarely associated with Kansas City, a lively heartland town with a reputation for order. But a closer look at the school board’s recent history reveals a chaotic, almost nonfunctioning body that put off making tough choices and even routine improvements for generations. Experts said that in the board’s years of inaction is a cautionary tale for school districts everywhere.