Educators say it is unfair that the quality of a child's schooling is an accident of geography, and that the neediest students often attend the poorest schools.

But they have a hard time proving whether more money translates directly into a better education.

"If you ask is there a correlation between the amount of money spent and student achievement, it is very small," said Robert Slavin, an educational researcher at Johns Hopkins University. "But there are a lot of things known to be very effective that cost money."

One of the biggest disputes has to do with class size. Teachers and parents contend that the smaller the class, the more attention a child can receive. But research has shown that, if everything else is equal, there is little difference in children's performance whether there are 25 or 30 students in class. Even the difference between 15 and 25 children is not that significant.

When schools have more money, they invest it in ways that do not always directly improve reading and math test scores. A more affluent school may have better art and music classes, more field trips, and sophisticated technological gear, such as cable television or video cameras.

It is hard to quantify the benefits of such amenties. But many educators, and a growing number of judges and politicians, believe they should be available equally to a state's public school children, regardless of whether they live in an affluent community or a poor one.

Compared with some states, the financial disparities among Maryland's school systems are not extreme. There is a gap of nearly $2,000 a student between Montgomery County, the state's most affluent school system, and Caroline County, the poorest. The gap in Virginia is about $4,700.

Nevertheless, the disparity in Maryland has doubled since 1978, when four poor school systems, including Caroline, lodged an unsuccessful suit to secure a bigger share of the state's education subsidies. And the gap has widened, despite state efforts since the mid-1980s to divert more money to the neediest school systems.

John Augenblick, a Denver consultant who has worked on several recent school finance lawsuits, said any difference of more than $600 "is worth looking into."

"The fact is, the rich are richer and the poor are poorer," said David Hornbeck, an educational consultant and Maryland's former school superintendent. "It is at least unequal and, I think, unjust and immoral to continue to do that."