WASHINGTON, July 8 - Margaret Spellings, the education secretary, suggested on Friday that the federal No Child Left Behind law, which requires that public school children be tested in reading and math, could be expanded to include other subjects.
"I am a strong believer in this, 'what gets measured gets done' kind of notion," Ms. Spellings told members of the American Federation of Teachers at their summer meeting here.
While she was referring to testing for science, which begins in two years, she added, "It helps the system figure out what we need to do, where and when."
She added, "And so, we need to round out the system a little more."
Expanding the federal testing requirements to include subjects beyond reading, math and science, however, would appear to require Congress to amend the law.
Ms. Spellings's comments came in a rare unscripted event for a senior member of the Bush administration. She shared a stage with the union president, Edward J. McElroy, who posed questions based on written queries submitted in advance by teachers at the meeting.
Describing himself as a union president eager to forge a friendly working relationship with Ms. Spellings and her staff, Mr. McElroy was largely solicitous of his guest, asking her only general questions and not pressing her for too many details.
His deferential manner came a day after his speech to the union in which he said teachers were expressing "incredible frustration" with the No Child Left Behind law "because of the way it's been implemented." Three-quarters of teachers responding to a union survey expressed unhappiness with the law, he said.
For the coming school year, states are required to test all children in Grades 3 through 8 and those in the 10th, 11th or 12th in reading and math. By the 2007-8 school year, states must be ready to begin testing children in science.
The possibility that testing might expand arose as Mr. McElroy asked Ms. Spellings to respond to criticism from teachers that an emphasis on math and reading was undermining the quality of education in other subjects, like civics and languages.
"I've heard that before about the testing issue," she replied, adding, "In many ways we're in the infancy of accountability and education in our country."
Speaking to reporters later, Ms. Spellings said the ability to expand testing depended upon refining the process of how children are measured.