PORTLAND, Ore. -- The math isn't so hard when it comes to the faculty of the Tigard-Tualatin school district.

This year, the district employs 640 teachers on a full-time equivalent basis. That's 56 fewer teachers than than a year ago. That's also 55 more teachers than the district would have had without the stimulus money provided by the federal government and dispensed by the state Legislature.

"We're really grateful for that federal funding," said Susan Stark Haydon, a spokeswoman for the suburban district southwest of Portland.

She and her district are hardly alone. The biggest share of spending from the federal economic stimulus package has gone to pay teachers, in Oregon and elsewhere.

But while the stimulus spending from what's called a "stabilization fund" has kept a couple thousand Oregon teachers in the public elementary and secondary classrooms, it hasn't brought stability to the school districts and probably couldn't.

The hit Oregon state government took in revenue during the Great Recession was, proportionally, one of the largest in the country, and the largest single part of the state government's budget is school aid.

A recent stimulus report from the U.S. Education Department listed Oregon among six states that suffered "catastrophic budget shortfalls." The others were Arizona, California, Florida, New Jersey and Wisconsin. To patch Oregon's budget, Oregon legislators spent stimulus dollars and raised taxes on business and wealthy people.

Even so, a survey conducted by three groups of school administrators found that as state school aid fell by 4 percent, the number of teachers employed in Oregon classrooms is down by 6 percent and class sizes are up by about two students each.

"Even with those stimulus dollars, we still had layoffs," said state Schools Superintendent Susan Castillo. "Without them, we would have had even more."

In many cases, Oregon school districts said in reports to Castillo's department that the stimulus dollars forestalled cuts: They didn't have to cut last school year short, or they didn't have to lay off as many teachers as expected, such as in Tigard-Tualatin.

How that played out varied from district to district.

In Ontario in Eastern Oregon, for example, a successful program that uses specialists to coach teachers of reading and writing courses was on the chopping block during the budget-writing earlier this year. The program had begun a few years ago with a federal grant, said spokeswoman Sidni Mordhorst. When the grant ended, school leaders were impressed with the results, so they worked the expense into its regular budget.

As a new expense, though, it was vulnerable when school leaders started making the current budget.

Then along came the stimulus money. It saved the six positions, Mordhorst said.

"Tooth and nail, we were holding on to those positions that make such a vital difference in the way we do business," she said.

The stimulus program counts jobs either "saved" or "created." In the general run of teachers, staff and administrators, most Oregon schools were holding on to jobs as best they could, as in Ontario.

In that category, the state Education Department counts 2,811 jobs saved or created.

The federal government also earmarked stimulus money for school programs for disadvantaged or special education students. Oregon districts reported nearly 1,000 jobs saved or created from this spending, and expanded offerings were more common.

From the special education stimulus money, for example, the Harney County school district hired a psychologist, "the first time the District has been able to do this," according to its report to the state.

Employing two teachers and six assistants full time, the Lake Oswego district began programs this fall for high-functioning autistic pupils in grade school, such as those who have Asperger's syndrome. The idea is to coach them in social communications and executive functions such as planning, so that they can succeed in the classroom, said Patrick Tomblin, Lake Oswego special education director.

The new programs, serving 21 young people, are an extension of similar programs in upper grades, where the success has been marked and discipline referrals are way down, Tomblin said.

The federal stimulus program is designed to be temporary, lasting three years, which means that soon Tomblin and educators throughout the state will again face questions about what parts of their curriculum and services to keep and what to jettison.

Tomblin said he's determined to keep the programs for autistic pupils, which could cause changes elsewhere in his operation, such as higher caseloads for the staff. "We may have to make some hard decisions," he said.

How to replace the temporary stimulus money is part of a larger budget puzzle for educators in Oregon, noted for wide swings in school finance because state aid is tied so closely to income tax revenue.

Craig Hawkins, a spokesman for the Confederation of Oregon School Administrators, said the level of uncertainty is even higher than usual.

A referendum vote in January on the tax increases is the immediate question. If voters reject the taxes, many schools are expected to shorten the current school year. There are smaller worries, such as an impending jump in pension contributions.

Beyond that is a more worrisome question: Will an anemic recovery that creates few jobs continue to starve state tax revenue and tear away at school districts?

"There are a lot of unknowns out there," Hawkins said, "and not a lot of positive signs about them."