I was sort of expecting you to share where you got that from. Never mind.
When I googled it this morning
https://www.google.com/search?num=50&si ... h0pQ_GV_GIthe top 4 results weren't that impressive.
1. American Schools vs. the World: Expensive, Unequal, Bad at Math
2. Globally Challenged: Are U.S. Students Ready to Compete?
3. National University Rankings | Top National Universities | US News
4. Why Can't U.S. Students Compete With the Rest of the World?
Forgetting about the top 25% for a while let's focus on the bottom 75%. It kinda sounds like you are saying that 75 percent of US students are below average. Google seems to agree. Shouldn't that number be 50%? Sounds like a common core math problem if you ask me!