The brunt of TRIM, Prince George's County's property tax limit, has fallen on the schools and therefore on the county's children. Whatever else TRIM may or may not have achieved, that is the central point. The recent articles by Michel McQueen and Margaret Shapiro reviewed the consequences of this rigid restraint on tax revenues. Some of the other effects, like the high mileage on superannuated police cars, may stick more easily in the mind because they can be more easily measured. But the ratio of teachers to pupils is now far lower in Prince George's than anywhere else in the metropolitan area. In the past four years the county has eliminated 2,700 jobs. Of them, 2,560 were in the schools, mostly teaching positions.

It's fair to argue that expenditure on a school system is not always proportional to its quality. There are still many highly competent and devoted teachers in the Prince George's system. But no one contends that there's no relation at all between spending and quality.

TRIM, enacted in 1978, is an unusually drastic hold-down. It forbids the county to collect more in property taxes than it did in 1979. When new construction is added to the tax base, tax rates must fall. There is no provision for inflation, and the purchasing power of the dollar has dropped by one- fourth since 1979. The effect of this decline was veiled at first by increased federal and state aid. But federal aid is now declining, and the state, with some justice, fails to see why it should make special efforts to help a county that won't help itself.

The county's voters clearly continue to like TRIM, and to consider it a safeguard against an ambitious county government that seemed to them to be getting out of hand. An amendment to loosen the restriction was beaten decisively in the election last November, and, in a poll published yesterday by this newspaper, the support for TRIM was still strong. But it was interesting to see, in the same poll, that 61 percent thought that it was going to have to be changed soon. More than half said that they would prefer an increase in property taxes to further cuts in services. Not many people thought the schools were improved; more thought them doing a worse job, or the same.

To the county's political leadership, those answers seem to offer a glimmer of possibility. Prince George's voters understand the impact of TRIM perfectly clearly, and they are evidently prepared to think about modification even if it means higher property taxes. But they want reassurance that the county council is not going to run away with the tax rate. Now it's up to the politicians to construct a formula that can bring some help to the desperately pressed schools, without raising new fears of open-ended tax increases in a time of tight budgets at home.