Arlington County is immersed in a debate over middle-school schedules following the school system’s proposal to double the length of some classes.

In December, Superintendent Patrick K. Murphy proposed “block scheduling” in middle schools. The plan would lengthen most core academic classes to 76 minutes for sixth-graders and 93 minutes for seventh- and eighth-graders, up from an average of 45 minutes. Every day except Monday, which would keep the standard seven-class schedule, students would go to fewer but longer classes, with subjects alternating daily.

Murphy had intended to seek school board approval in March. But because many parents had questions, the timetable was moved to May. Although the plan may end up changing, block scheduling is not off the table.

“There might be some kind of restructuring,” Margaret Gilhooley, assistant superintendent of instruction, said Monday. “Whether it’s block or something else, we’re not quite sure yet.”

Arlington Parents for Effective Scheduling in Schools, formed in response to the proposal, says it is worried about a potential for larger class sizes and the impact on non-core classes, such as music.

“It definitely will have a decrease in participation in the arts,” said Susan Scott, whose daughter plays in the band at Thomas Jefferson Middle School. “They need to look at the inadvertent damages.”

Block scheduling is fairly common in high schools, and it is sometimes found in middle schools. In Fairfax County, 17 of 26 middle schools use some form of block scheduling.

But some question its effectiveness. According to a study published in the April/May issue of High School Journal, students who had block scheduling in high school performed no better in college science courses than peers who had traditional schedules.

“The students who had block scheduling fared slightly worse in many cases,” said University of Virginia professor Robert Tai, who co-authored the study. “It may actually be exacerbated at the middle school level.”

Tai said one challenge is communication between administrators and teachers. Transitions to block schedules are often swift, giving teachers little time to prepare new lesson plans.

“The teachers tend to go to what they perceive to be the most efficient method, which is lecture-style,” Tai said. “If you’re thinking of shifting to make things better, things will be worse in the short run and generally unchanged in the long run.”

Murphy said he plans to meet with teachers at every middle school. He also has held community forums, staff meetings and an online town hall event.

“I wanted to hear their voice on the issue and see what they think,” Murphy said. “It’s all very transparent.”

Tom Mallan, who has children in the fifth and eighth grades, said he worries that the superintendent will advance with the plan despite community opposition.

“There’s skepticism around this one,” Mallan said. “I have high hopes, though — I hear somewhat of a change in tone.”

Murphy’s staff plans to continue to gather feedback through March before acting on a proposal.

“It may play out differently depending on the school,” Gilhooley said. “Block scheduling is not a done deal.”