Duncan called on Congress to fix the law before the next school year so the schools and students most at risk of failing receive the assistance they need.
"No Child Left Behind is broken and we need to fix it now," Duncan told the House Committee on Education and the Workforce.
"This law has created a thousand ways for schools to fail and very few ways to help them succeed. We should get out of the business of labeling schools as failures and create a new law that is fair and flexible, and focused on the schools and students most at risk."
No Child Left Behind sets annual standards for all public schools to meet with the goal of having all students 100 percent proficient in reading or language arts and math by 2014.
Duncan said while NCLB exposed achievement gaps among poor and minority students, students with disabilities and English learners, the law requires states and districts to implement the same set of interventions regardless of the individual needs and circumstances of those schools.
Duncan said the Obama administration proposes reforming No Child Left Behind to recognize and reward high-poverty schools and districts that show improvement based on progress and growth. States and school districts would have to intervene in schools that persistently fail to close gaps, and would have more flexibility to deal with schools making modest gains.
"Our proposal will offer schools and districts much more flexibility in addressing achievement gaps, but we will impose a much tighter definition of success," Duncan said. "Simply stated, if schools boost overall proficiency but leave one subgroup behind -- that is not good enough. They need a plan that ensures that every child is being served."