Parent-teacher organizations throughout Prince George's County are leading a petition drive to raise the voter-imposed property tax limit in an effort to provide more money to the county's financially strapped schools.

Massive cuts in the county school budget resulting in the recent layoff of 507 teachers and systemwide cuts in school programs have given the "Plus 4" charter amendment new impetus, according to supporters. A coalition of PTAs, with the strong assistance of the county teachers' union, has collected more than 8,500 of 10,000 signatures needed to put the "Plus 4" amendment before the voters this fall, according to William T. Flahive, vice president of the county council of PTAs.

"I've gotten more calls in the last two weeks than the last two months," said Flahive, who hopes to amass at least 12,000 signatures at his home before the Aug. 16 deadline for placing an item on the ballot. "A month before it looked like everything was dying out," Flahive added.

TRIM (Tax Reform Initiative by Marylanders), a 1978 charter amendment, set an absolute limit of $144 million on property tax revenues collected by the county. Because inflation and new construction of houses and businesses have increased the assessed value of county property over the years, the overall property tax rate has been reduced to keep collections within the TRIM limit.

"You build the new house and you expect to have schools, police and fire departments. All those services have to be stretched for you and you're not paying as much for it," Flahive noted.

Tight budgets under County Executive Lawrence J. Hogan have kept tax collections below the TRIM limit since 1978. The property tax rate has been cut from $3.31 per hundred dollars of valuation in 1978 to $2.63 for the coming year.

But this year, collections reached the dollar limit set under TRIM for the first time. Many county observers predict that inflation and the hidden effects of the TRIM restrictions on county services will make next year's budget problems worse.

But County Executive Hogan said an amendment is not needed, at least not in the coming year, because cost-saving measures will allow the county to operate under the tax-collection limits.

The Plus 4 amendment, if approved by a majority of voters in November, would raise the limit on property tax collections to account for the value of new construction at the existing tax rate. In addition, it would allow the County Council to raise the TRIM limit by up to 4 percent in a given year. Supporters, including the police, firemen and unionized county workers, note that the measure would raise only $7 million to $8 million more in revenues next year, an amount that would only raise the current school budget only 2.6 percent. Its critics note that inflation alone would far exceed the help that the amendment could bring.

"This isn't going to solve all our problems, but it will help," said Diana McCusker, president of the county council of PTAs. "The most important thing is the attitude of the people," she added.