How could both these findings be accurate? Was it true, as NAEP results indicated, that U.S. 4th graders couldn’t walk and chew gum at the same time? Or was IEA’s conclusion—that the performance of American 4th graders in an international context was first class—more valid? A broader question arises here, one that has intrigued researchers for years: How would other nations perform if their students were held to the NAEP achievement-level benchmark for “proficient”? How might they perform on Common Core-aligned assess-ments with benchmarks that reflect those of NAEP?