President Bush's education law is prodding schools to help more needy students, but states will not come close to reaching all the struggling children unless the government spends more and lightens demands, an independent analysis says.

The No Child Left Behind Act (search) is turning up positive signs and warning signs in education, according to a review by the Center on Education Policy (search). The report released Wednesday is considered the most comprehensive review of the three-year-old law.

States are doing more to help students succeed in reading and math, aligning classes to state standards and using test data to identify weaknesses of children, the review found. The law is also spurring more teamwork among teachers and more focus on minority children.

Yet researchers said any success will be hindered unless problems are fixed.

Beyond their concerns about money and staffing, many school leaders say the testing requirements for disabled children and limited-English learners are unfair and unworkable. About one-half or more of the surveyed school districts say they have cut teaching time in social studies, science, art, music and other subjects to meet demands in reading and math.

Also, most school leaders have no idea whether there is any benefit to letting students in struggling schools get a transfer or a tutor, as the law allows. The private tutoring has so little oversight that it "has the earmarks of a scandal" said the center's president, Jack Jennings.

The study does not answer a central question of whether the law helps more students learn.

Most states and districts say student scores on reading and math tests are rising and that achievement gaps between white students and minorities are closing. But Jennings said there is no clear cause and effect between the law and the rising scores.

The law identifies problems well, he said, but is weaker in "providing the tools for educators to deal with those problems," Jennings said. "Unless we have a better balance, we're in danger of not being able to achieve the goals."

The Education Department is expected to give states additional flexibility, perhaps in the area of testing special-education students.

The law signed by Bush in 2002 is considered the most significant in federal education in 40 years. In particular, the law aims to ensure all minorities and poor children can read and do math at grade level by 2014.

The report is based largely on surveys of education officials from 49 states and 314 school districts, plus case studies in 36 districts. Oklahoma chose not to take part, and the District of Columbia responded too late to be included, Jennings said.

Assistant Education Secretary Ray Simon said he expects the trend of rising student achievement to continue as states and districts keep enforcing the law.

Simon credited Bush for increasing education spending and said, "The perpetual cry of more money, once again echoed in this report, simply does not comport with the facts."

He added: "The difference is that this administration is holding states accountable for delivering results with those taxpayer funds."

Schools face requirements to test many children yearly in reading and math, and to get a highly qualified teacher in every core class. They must report student performance by race, ethnicity and other categories so underperforming students do not get lost in school averages.

But the center's director, Patricia Sullivan, said the government must offer more help because "state education agencies are not designed -- either with staffing, funding or expertise -- to do the work that needs to be done to turn around low-performing schools."