Updated

President Bush said Monday that if Congress doesn't reauthorize the No Child Left Behind education law, he'll make as many changes as he can on his own.

Bush also said that if Congress does renew the law but weakens it in the process, he'd "strongly oppose it and veto it"

That scenario seems unlikely for now, since the top Democrat and Republican on the Senate Education Committee have said they would put off rewriting the six-year-old law until later this year.

The law requires math and reading tests in grades three through eight, and once in high school. Schools that miss testing benchmarks face increasingly stiff sanctions. Bush regards the law, which took effect in 2002, as one of the signature domestic achievements of his presidency, and sees expanding it as key to his legacy.

If the law isn't revised by Congress, the existing law stands.

There is broad agreement that it should be changed to encourage schools to measure individual student progress over time instead of using snapshot comparisons of certain grade levels. There also is a consensus that the law should be changed so that schools that miss progress goals by a little don't face the same consequences as schools that miss them by a lot.

But deep divisions remain over some proposed changes, including merit pay for teachers and whether schools should be judged based on test scores in subjects other than reading and math.

Many educators and lawmakers who once supported it now say the law has failed to live up to its promise. One of the law's lead original authors, Democratic Sen. Edward Kennedy, defended it, praising what he said are modest improvements that have seen so far. But in an op-ed published in The Washington Post, Kennedy ticked off a series of needed reforms.

Most of all, Kennedy called it "disgraceful" that Bush — his former partner in passing the law — has failed to include adequate funding for school reform in his education budgets. "Struggling schools can do only so much on a tin-cup budget," Kennedy wrote.

"Clearly I don't agree with that," responded Education Secretary Margaret Spellings, who traveled with Bush to Chicago. She said federal education funding is up about 46 percent since Bush took office.

Bush laid out what he said were some changes he would consider making administratively if lawmakers fail to act: ensuring "that a high school degree means something," increasing flexibility for states and school districts, providing extra help for struggling schools, and devising an accurate system for measuring high school dropout rates.

"There are things we can do, and must do, by working together," he said during an appearance at Horace Greeley Elementary School in Chicago.

"I believe the country needs to build upon the successes" of the law, Bush said. "It's not worthwhile to guess when a child's future is at stake."

Greeley was chosen as the backdrop for Bush to commemorate the sixth anniversary of the law's signing because the school has thrived under the No Child Left Behind Act.

The school, where 70 percent of students are Hispanic and 92 percent are low-income, was named a Blue Ribbon School under the program in October, one of just 12 public schools in the state and 239 across the country. Since 2005, 83 percent of Greeley students have met or exceeded state standards, compared to an average of 64 percent for the entire Chicago Public Schools system.

"In fact, Chicago is an example of NCLB's lack of effectiveness," said Dr. Monty Neill, an NCLB critic and executive director of the National Center for Fair & Open Testing. "The law has failed to raise academic achievement significantly in that city, in other major urban areas or in the nation as a whole."

Also Monday, a federal appeals court revived a lawsuit challenging the law's funding.

The lawsuit argues that schools should not have to comply with requirements that aren't funded by the federal government. Plaintiffs include the Pontiac, Mich., school district and eight districts in Texas and Vermont, along with National Education Association affiliates in several states. The NEA, the nation's largest teachers union, is paying the cost of the appeal.

Chief U.S. District Judge Bernard Friedman in Detroit dismissed the lawsuit in November 2005, but his ruling was reversed by a three-judge panel of the 6th U.S. Circuit Court of Appeals in Cincinnati in a 2-1 decision released Monday.

Bush is slated to discuss the economy at a separate event Monday afternoon in Chicago. He also gave a boost to Chicago's bid to host the 2016 Summer Olympics, appearing briefly for pictures with members of the bid committee. The finalists are to be chosen in June by the International Olympic Committee and the winner will be announced Oct. 2, 2009.

"I can't think of a better city to represent the United States than Chicago," Bush said. "Our hope is that the judges will take a good look at Chicago and select Chicago for the 2016 Olympics."