HARRISBURG — School boards may not cut the compensation of tax collectors to the point where the reductions prevent them from performing their duties, the Pennsylvania Supreme Court said Monday.

The high court ruled unanimously that two suburban Philadelphia districts went too far when they sharply reduced the rate by which their tax collectors are paid, imposing cuts of 69 percent and 79 percent.

“We recognize the difficulties faced by the school boards in periods of financial uncertainty, but it is beyond the boards’ power to transform the local tax collection system by reducing compensation levels to such a degree that the elected tax collectors are unable to fulfill their responsibilities,” wrote Justice Thomas Saylor. “Such systemic change must come from the Legislature.”

Fifteen tax collectors in Bucks County sued the Pennridge and Central Bucks school districts after they passed resolutions in 2009 that cut their compensation, which is based on a per-bill fee. A county judge sided with the tax collectors, but a Commonwealth Court panel reversed the ruling in 2010, saying the collectors did not prove the changes were arbitrary and capricious.

A Pennridge administrator said the district was considering a cost-saving move to a “lockbox” system where taxpayers would not go through a tax collector. Central Bucks hoped to give the business to a commercial tax-collection agency, which was estimated to save more than $100,000 annually.

“While school boards have a duty to the public to set and meet their budgets, altering the method of tax collection favored by the General Assembly as a means of doing so is beyond their authority,” Saylor wrote.

Justice J. Michael Eakin wrote in a concurring opinion that while he agreed with the five other justices, there was a difference between pay cuts that prevent the collectors from performing their statutory duties, which would be illegal, and cuts that would address customer services.

“Customer service is a very nice thing,” Eakin wrote, “but when tax dollars are tight, it is a luxury item” that boards may eliminate.

Attorney Howard Kelin, who represents the districts, said the ruling meant that a district had no choice but to pay collectors based on the amount of hours worked, whether they use technology to expedite the work and whether they are efficient or inefficient.

“In other words, the Supreme Court is saying school districts must pay more for inefficient tax collection than for efficient tax collection,” he said in a statement. “That surely was not the intent of the General Assembly.”

Lawyers for the tax collectors did not return phone messages seeking comment late Monday.