When Mayor Thomas Menino announced the formation of the “External Advisory Committee on School Choice” last February, he made its mission clear in the press release naming its members: To “help advise” the school department in engaging the community on a major overhaul of the city’s school assignment system.

Flash forward to the end of November, when Menino’s office said the 27-member group’s deadline for finishing its work would be pushed past December and into mid-January: The extension will allow it more time to analyze data as “it creates an improved student assignment system,” the notice said, in an apparent acknowledgement of the committee’s increased responsibility in crafting changes to the system.

The track laid out for the advisory committee almost a year ago remains the same. The committee is expected eventually to present changes to the system to Superintendent Carol Johnson, who will then take them to the mayorally appointed School Committee.

Johnson, the school department and the School Committee have the ability to tweak any recommendation sent their way, of course. But at recent meetings of the advisory panel, changes in its role were apparent, as the committee pulled together the strands of the various proposals while school department officials weighed in by providing both advice and data.

The advisory group – co-chaired by Hardin Coleman, the dean of Boston University’s School of Education, and Helen Dajer, a former School Committee member – has grown in power and influence, steering the discussion and eyeing complex plans like the one developed by a Massachusetts Institute of Technology doctoral student and another offered by City Councillor At-Large John Connolly and several other elected officials that would eliminate zones and set up a network of city-wide “magnet” schools.

The advisory committee is also expected to take up the politically dicey issue of whether to grandfather siblings when the department implements changes to the system. Current students will be grandfathered, a decision the school department made after parental outcry earlier this year.

The much-maligned existing system, in place for the last 25 years, splits the city into three zones, which comes with the transportation costs of busing children from one end of the city to the other.

For his part, Menino has given the committee, which meets again tonight (Dec. 13) at 6 p.m. at Suffolk University, a wide berth. He is allowing the advisory committee additional time to wade through the data, despite the tighter timeline initially raised in his 2012 State of the City address, where he said that the city will have a plan by his 2013 address.

Earlier this fall, after the school department proposed five plans, Menino was asked if there were any proposals that should be off the table. He pointed to the no-zone and 23-zone proposals.

Hours later, there was a shift in tone, with the mayor telling another reporter that “somewhere in between” lies a plan for improving the school system.

The administration has stuck to pushing for change in the system, in the general sense, and leaving it to the committee to make a specific solution. City officials have frequently taken to pointing out that the 1,193 K-8 students who live in the Bowdoin-Geneva neighborhood are bused to 64 schools, from Hyde Park to South Boston. The figure has been used in columns and in a video mapping the distances that the mayor’s office released this week.

And at least one public meeting about the proposals, school officials made a presentation that highlighted the frustrations that parents have with the current system. To close observers of the 2009 mayoral race, those frustrations resembled the criticism that was lobbed into the campaign by then-challenger Michael Flaherty, to the administration’s chagrin.

Asked about the committee’s accumulation of power, one of its members pushed back on the notion. “The role we have and charge we have has been consistent throughout,” said Robert Gittens, who lives in Dorchester and works for Northeastern University. He said people may have expected the group to make a quick decision, “but what is now happening is we’re digging even more deeply” to come up with the best plan.”

The group has not done a poll, so it’s not clear where, or if, there is a consensus on what to do.

Gittens said the group’s goal remains: Finish its work in January. “But we want to get it right. So we’re working hard to make that happen.”