The Organization for Economic Co-operation and Development (OECD) released the results of its 2015 global rankings on student performance in mathematics, reading, and science, on the Program for International Student Assessment, or PISA.

The PISA is a worldwide exam administered every three years that measures 15-year-olds in 72 countries. About 540,000 students took the exam in 2015.

The US saw an 11-point drop in average score for math, while remaining relatively flat in reading and science.

Business Insider

The results again raise questions about the global competitiveness of the US educational system.

On a press call on Tuesday, Jon Schnur, executive chairman of America Achieves, said we need to make dramatic progress in showing educational improvement for students.

When looking at a comparable sample of countries that participated in the PISA exam in both 2012 (the last time the test was administered) and 2015, the US ranking fell to 35th from 28th in math. The US underperformed the OECD average in math.

Scores were relatively unchanged in reading and science compared to 2012 — down one point in each. The US performed better than the OECD average in both subjects.

Asian countries again topped the rankings across all subjects, and Singapore was the top performing country across all three subjects.