OECD and Pisa studies
The final results will be published on Dec 4th 2007 but here's what to expect:
The PISA survey is the most comprehensive and rigorous international yardstick of secondary-school students' attainments. PISA 2006 was held in 57 countries that together account for nearly 90% of world GDP. It tested students on how much they knew about science and their ability to use scientific knowledge and understanding to identify and address questions and resolve problems in daily life. It also examined student performance in reading and mathematics, and collected data on the student, family and institutional factors that can help explain differences in performance.
http://www.pisa.oecd.org/document/40/0,3343,en_32252351_32235731_39701864_1_1_1_1,00.html
In short - we have the worlds smartest teenagers!