HARRISBURG — Two-thirds of Pennsylvania’s 501 school districts plan to limit property-tax increases next year to the rate of inflation.

That’s the finding of a state Education Department report released yesterday.

The annual report to state lawmakers said 336 districts had either adopted preliminary spending plans for the 2007-08 fiscal year that would keep tax increases at or below inflation, or passed binding resolutions expressing that intention.

Under a 2006 law aimed at cutting property taxes for homeowners, districts must keep increases within an inflationary index, starting with the 2007-08 budgets now being finalized. This year, the indexes vary by district from 3.4 percent to 5.5 percent.

Larger tax increases must be placed on the May 15 primary ballot — unless school boards can convince state officials or a county judge that the increase is justified by factors such as the costs of special education, health insurance or pensions.

“We’re pleased that the law seems to be doing what it is intended to do — that two of every three school districts are keeping their tax increases within the rate of inflation, and that most of the others are forced to raise taxes for costs beyond the school board’s control,” said Chuck Ardo, a spokesman for Gov. Ed Rendell.

Although the state has given 210 districts the option to impose higher tax increases without seeking voter approval, 52 of those districts approved preliminary budgets with inflationary increases, according to the report.

Scott Shewell, spokesman for the Pennsylvania School Boards Association, noted that some of those districts may use their exceptions when they adopt final spending plans by June 30.

“Some of those 52 districts might, upon reflection, have to make a change, which is why they filed for the exceptions,” Shewell said.

One critic of the law, Matthew Brouillette of the conservative Commonwealth Foundation, said voters should be allowed to approve any property-tax increase, no matter how small.

“The generosity that exists in the law ... does not likely give any comfort to taxpayers whose property-tax bills are going to go up irrespective of the decision of the districts,” Brouillette said.

The report did not say how many school districts were granted exceptions by county courts.

The current law promises to deliver up to $1 billion in property-tax cuts a year financed by slot-machine gambling. It replaced a similar 2004 law that allowed local school boards to decide whether to operate under stricter taxing constraints in exchange for accepting a share of the gambling revenue.

The old law, known as Act 72, failed because only 20 percent of the school districts agreed to do so.