It's one heck of a public relations challenge — persuading Lower Merion taxpayers to give a raise to the highest-paid teachers in the state.

On the opening day of school Tuesday in one of the wealthiest, top-rated districts in Pennsylvania, the Lower Merion Education Association is asking the public to sign an online petition that asks the school board to give teachers a "fair contract."

The petition — at − says Lower Merion teachers go above and beyond in their service to students yet have received raises averaging only a half to 1 percent annually over the last seven years.

"It's just not fair," the petition said.

LMEA's two-year pact expired June 30, and union president Chris Santa Maria said that this summer brought little progress in forging a new deal. The organization, which represents 772 teachers and about 660 support staff, has now hired a public relations firm, DDCworks in Philadelphia, to drum up community support.

"We needed the community to understand that we're part of the Lower Merion success story," Santa Maria said, "and that we're also very dedicated teachers."

And very well paid, according to state Department of Education data that list the average Lower Merion teacher salary as $99,253, the highest in the state.

School district officials have "been a bit taken aback with the aggressive stance of the LMEA," said school board president Robin Vann Lynch. "We've always worked very closely with them in a collegial manner."

Other area districts that are starting the school year without settled contracts are Norristown, Methacton, Coatesville, Tredyffrin/Easttown, and Springfield in Delaware County. Teachers have employed hardball tactics in the past to force districts to settle. In 2015, teachers in another Main Line district, Radnor, sent a letter home to high school parents saying they wouldn't write college recommendation letters until they got a new pact.

The labor impasse in Lower Merion comes at a time when the high-achieving Montgomery County district has been wracked by controversies over its fast-rising enrollment as well as a  lawsuit aimed at blocking property-tax hikes.

In the middle of this, the union insists it's time for a raise. Santa Maria said Lower Merion teachers earned their high salaries by being the best at what they did. Ninety-two percent of its teachers have master's degrees or higher, and 36 members hold doctorates.

One of the sticking points for Lower Merion, as well as other districts with longtime staff, is that when teachers reach the top of the salary scale after 13 years of service, they no longer get built-in annual pay hikes that are awarded for experience and education. In recent years, budget-tightening school boards have been loath to award much beyond those "step" increases.

Sixty-three percent of Lower Merion's staff have reached the salary ceiling and received the small pay raises, said Santa Maria. The rest of the staff received an average of 3 percent pay raises in each of the last two years.

Once teachers hit the pay ceiling, Vann Lynch acknowledged, "it does become more financially challenging for the district to offer high increases." But in the last contract, she said, those teachers got a 1.9 percent nonrecurring increase, essentially a bonus, that did not factor into their pensions.

In a statement, the school board took aim at LMEA's strategy, saying: "We are concerned that tactics that divide our community may prove counterproductive at a time when support for public education is already fragile."

One of the biggest concerns for school districts is rising pension costs. Across Pennsylvania, the rate of school districts' per-worker pension contribution, based on salary, increased this year from 30.03 percent to 32.57 percent.

The 8,400-student district also has experienced unprecedented growth and expects to surpass 9,300 pupils in the next 10 years. The district is also defending a lawsuit brought by residents — led by aviation lawyer Arthur Wolk — over a 4.4 percent tax increase for the 2016-17 school year.

Philip Browndeis, one of the three residents suing the district, wrote in an email: "I suspect that the LMEA will get pretty much everything it demands after the November election. At the April School Board meeting, [Vann Lynch] stated that she represents the students and families; she did not state that she represents all the residents of Lower Merion."

The lawsuit revolved around whether the district misrepresented its finances to skirt a state law that prevents school districts from hiking taxes more than 2.4 percent without going to a referendum. In August 2016, a Montgomery County judge ruled against the district, saying it had falsely projected annual multimillion-dollar deficits — and raised taxes —  when it actually had tens of million in surplus each year.

Santa Maria asked why the district couldn't use some of that stockpiled money to give teachers a raise, especially as Lower Merion wouldn't be so successful — and wouldn't be experiencing staggering growth — without the excellence of its teachers.

"There wouldn't be an enrollment problem in Lower Merion if Lower Merion schools weren't top-notch," he said. "They wouldn't be top-notch without the work we do. We're getting penalized for doing good work."