Agreement then becomes impossible, largely because there is no agreement on the facts, much less on their interpretation.
Curricula vary from country to country, and the sampling of students is fraught with problems.
Historical comparisons are also slippery. The decline of SAT scores has been well documented. Apparently we are doing a good job of producing Ph.D. mathematicians, and have a more than adequate supply. By this standard we are doing well. Few are satisfied with this level of performance.