President Bush on Tuesday began a three-day education tour, defending his initiatives against critics who say they hold schools accountable for big gains without enough money to succeed.

No child should be trapped in a school that does not teach and will not change, Bush told several hundred students, parents and teachers in the gym at Butterfield Junior High School.

"Under the new law, when we discover that children are falling behind — that are not meeting standards, those schools get extra help, extra money to make sure that people are brought up to the standards," Bush said. "Schools will have time to improve. ... But at some point there has to be an end to mediocrity."

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In his 10th visit to Arkansas, which he won in 2000 with 51 percent of the vote, Bush went to a Republican stronghold near the Oklahoma border. On Wednesday, in suburban Washington, Bush will speak about the importance of reading in early grades. And on Thursday, Bush will visit a high school in West Virginia, another election battleground.

Signed in 2003, the No Child Left Behind (search) education law was the centerpiece of Bush's domestic policy agenda. It mandated tough testing and gave all students until 2014 to become proficient in reading and math.

The legislation had bipartisan backing but has run into opposition from Democrats who claim Bush is enforcing the law on the cheap. Teachers unions argue that the president is taking credit for actions by Congress, which increased funding levels for education over and above what the president requested the past few years.

The law requires states to chart adequate yearly progress — not just for a school's overall population, but for groups such as minorities and students who speak little English. Sanctions grow by the year for schools receiving low-income aid that don't improve enough. Consequences range from letting students transfer to a better school within their districts to transferring control of a poor-performing school to the state.

Last month, the administration announced it was easing some testing provisions and other aspects of the law, including one that required teachers to have a degree or be certified in every subject they teach.

"A quarter of all Arkansas public schools were labeled this past year as failing to meet the adequate yearly progress provisions of No Child Left Behind — a number that is likely to rise rapidly as many schools find it impossible to meet the rigid requirements," said Sid Johnson, president of the Arkansas Education Association (search), a member of the National Education Association (search), the nation's largest teachers union.

"Nationwide, a growing chorus of teachers, parents, principals and state and local policy-makers have been raising serious, legitimate concerns about the law's one-size-fits-all approach to educating children and its lack of adequate resources. The Department of Education has responded to election-year pressure by tweaking the law, but it has left many of its fundamental problems unresolved," Johnson said.

Bush rebutted the criticism: "High standards do not set children on a path to failure. High standards set our children on the path to success."