U.S. math scores have not budged significantly since 2003 on the worldwide assessment.
High quality teaching is key to student success in high-performing countries and school systems, study finds.
More than 100 U.S. schools are using an international test of 15-year-olds to see how they stack up against others around the world.
PISA tests show a lower-than-average percentage of U.S. students were high-performing in math, while a higher-than-average percentage of U.S. students were below proficient in math last year.
