Delivering the final policy speech of his administration, President Bush today heralded his landmark education law and warned that it should not be watered down when he leaves office.

Speaking from the Kearny School auditorium in Northern Liberties on the seventh anniversary of the No Child Left Behind Act, Bush said that it "forever changed America's school systems."

The controversial law required states to set benchmarks and test students annually in reading and math, with a goal of all American schoolchildren passing the exams by 2014. Schools that fail to meet standards face penalties, and students who attend those schools have the right to transfer out.

Critics say the law is underfunded, too punitive, and makes schools focus narrowly on testing.

But Bush, speaking to an auditorium packed with parents, children and dignitaries, waved off such criticisms.

"How can you possibly determine whether a child can read at grade level if you don't test? And for those who claim we're teaching the test, uh-uh. We're teaching a child to read so he or she can pass the test," the president said.

The law - which requires schools to break down data by race and socioeconomic status - was designed to make sure the most vulnerable children don't slip through educational cracks, Bush said.

Those children are often "inner-city kids, or children whose parents don't speak English as a first language. They're the easiest children to forget about," the president said.

While some progress has been made nationwide in narrowing the achievement gap between white and Asian students and their Hispanic and African American peers, a wide gulf still exists.

Kearny, a K-8 school with a largely African American student body, was selected as the site of Bush's visit because it has passed state exams several years running, despite a high percentage of students living in poverty.

"We have come because this is one of the really fine schools in the city of Philadelphia," Bush said.

The president had pointed words for the Democratic Congress which is scheduled to reauthorize the law this year and for President-elect Barack Obama.

"In weakening the law, you weaken the chance for a child to succeed in America," said Bush.