SHIRLEY -- Underscoring the Finance Committee's take on a proposed Ayer-Shirley Regional School District budget that calls for a $900,000 assessment hike over last year, selectmen Monday night told Superintendent of Schools Carl Mock the town can't pay the bill without a tax override.

Summarizing the presentation he gave to the Ayer and Shirley Finance Committees and Ayer selectmen, Mock said the needs-based budget the School Committee approved in January reflected the district's determination to provide the kind of quality education kids need and deserve and that both communities want, rather than base the budget on "fiscal limits" in the two towns.

As proof the budget was realistic versus idealistic, Mock pointed to a wish list of items the administrative team submitted that totaled $1.8 million, noting an "unmet needs" deficit that continues to grow.

"We knew we might have to back down some," and they've started to look at ways to do that, he said. "But the need doesn't go away."

Mock listed "cost-drivers" behind an anticipated assessment of more than double the 4.88 percent hike Town Administrator Patrice Garvin built into the municipal budget. The biggest number was salaries, about $387,000 more than last year. Second was health insurance, up by $200,000. School choice-out numbers rose and the cost of transportation did too, plus additional utility costs for the new high school now under construction.

"We never said a new school would cost less," Mock said, only that it would be more efficient.

Over the last couple of years, "six figure" savings included shrinking Lunenburg tuition as the contract expires and past personnel reductions. But savings have been more modest this year and the trend will continue, Mock said. Three items to watch between now and Town Meeting are the cost of medical insurance, special education and facilities, particularly fuel bills, he added.

But Selectman David Swain wanted to spotlight the revenue side, in particular, how the school district can do more to promote itself, holding open houses to highlight programs and showcasing the renovated high school and new academic wing once the multi-million-dollar building project is completed.

It might take some repackaging and selling to recruit within the district, Swain said, to lessen the number of students leaving to attend other public school districts, choices that draw significant amounts of state money from the district.

Mock, who is leaving when his contract is up at the end of the school year, acknowledged that he might not have been much of a cheerleader but has preferred to let programs speak for themselves "I'd say more...it's a complex issue," he ventured, conceding that the dialog made him uncomfortable. But it's not all about PR, he said.

"It doesn't take long...to figure out" which communities commit the most resources to education, Mock said. And "bad press" about town and school officials squabbling over the school budget doesn't help matters any.

The town can't pay such a high assessment this year, although both sides agreed those are issues worth talking about now to resolve them for the future.

Garvin said indicators point to the School Committee seeking a tax override rather than back away from the $900,000 assessment increase, although they haven't said so yet.

Selectmen certainly showed no such inclination, nor did the Finance Committee, when Mock and other school officials made a similar presentation to them last week. Chairman Mike Swanton said then that it was not the time to ask for an override, with the debt-exclusion hike for the high-school project set to hit town tax bills next year.

In terms of an override, the numbers would be "significant," Garvin said, citing a spreadsheet prepared by Principal Assessor Rebecca Boucher and based on an override of $200,000.

With the normal levy increase per Proposition 2 1/2, plus the debt-exclusion payment for the ASRSD High School project, and a $200,000 tax override that would allow the town to meet its school assessment, the town tax rate would rise by $1.41 per $1000 of value and increase the average tax bill by 8.41 percent. The "total effect" would be that taxes on an "average" ($251,113) home would rise $353.57, according to Boucher.

Citing cuts the town has made to balance its budget, Garvin indicated the School District should follow suit.