Forty-six states-representing 80 percent of the nation's K-12 student population-have formally agreed to join forces to create common academic standards in math and English language arts through an effort led by the National Governors Association and the Council of Chief State School Officers.

The four states not on board, as of last week, were Alaska, Missouri, South Carolina, and Texas.

"This is a giant step," said U.S. Secretary of Education Arne Duncan, who has been pushing stat...