WASHINGTON — Poor children in public schools are shortchanged by federal and state school aid policies, a report released yesterday says.

The federal Education Department gives states nearly $13 billion a year to help students in low-income districts.

The complex formula used to determine each state's share guarantees a minimum amount for small-population states. That means Wyoming and Vermont, for example, can get more money per poor student than do more populous states.

Federal school dollars also are tied to the amount that each state spends on education. States that spend more get more from Washington.

But this link rewards states more for their wealth than their efforts to educate poor kids, according to the Education Trust, a Washington-based children's advocacy group.

For example, the report shows Maryland has fewer poor children than Arkansas but gets about 50 percent more federal aid per poor child, $1,522, than does Arkansas, at $1,009.

The report shows that Hawai'i ranks 25th in the nation, with 26,720 poor children, who receive an average of $1,351.

The gap occurs even though Arkansas dedicates a larger share of its resources to education than does wealthier Maryland, the report says.

The authors say that when Congress reviews federal education spending in the coming year, lawmakers should rethink how they distribute money for poor students.

Poor children were defined as those living in households with incomes below the federal poverty line of $18,660 for a family of four in 2003.