More than a fourth of the nation's schools failed to meet the requirements of the No Child Left Behind Law last year, according to preliminary numbers reported to the Department of Education.

About half the states increased the number of schools making "adequate yearly progress" in improving student test scores in math and reading in the 2004-05 school year. Overall, 27 percent of the schools failed to show adequate improvement, up one percentage point from the year before.

"This is just one piece of data we look at," said Chad Colby, a spokesman for the Department of Education. These numbers alone don't signify a trend in how schools are doing, he said Wednesday. "This isn't a trend indicator in proficiency."

Schools receiving federal poverty aid can be sanctioned for not making "adequate yearly progress" two years in a row, with administrators and teachers eventually being replaced.

To meet goals, schools must show overall improvement, plus gains by minority students, poor students, students with limited English skills and students with disabilities.

States are required to get increasing percentages of students proficient in math and reading, with all students being proficient by 2013-14.

However, states are given flexibility in designing tests, and many have made it easier to meet federal requirements.

The result is an uneven measurement from state to state, said Joel Packer, a lobbyist for the National Education Association, the country's largest teachers union.

"Each state has its own standards, each state has its own tests, each state has its own definition of what it means to be proficient," Packer said.

Oklahoma led the country in 2004-05 with 97 percent of its schools making adequate progress. It was followed closely by Rhode Island, Iowa, Montana and New Hampshire.

Florida was at the bottom, with only 28 percent of its school meeting the requirements. Hawaii, Nevada, New Mexico and South Carolina rounded out the bottom five states.

Ross Wiener, policy director at the Education Trust, a Washington research and advocacy group, said states can do better if they address funding and teacher inequities. Wiener said too many poor school districts get less money and less qualified teachers than wealthier districts.

"We have not taken a lot of steps that could dramatically improve student achievement," Wiener said.