Still, somewhat ironically, you are both right. Underperforming ethnic groups in the US bring the average down, and the US educational Prime Directive of making sure the high-performing groups don't get ahead brings it down even farther. While Asian schools work hard to push Asian kids ahead, US schools refuse to do so, because that would just widen "the achievement gap" they're trying so hard to close. So US schools, first in spending, are last in effectiveness for ethnic Asian kids. That "doing the least with most" is school underperformance. The only reason Asian-American kids do as well as they do is that, like their cousins in Asia, they get a lot of their education outside of school.
 2007 TIMSS results:
Asian scores are on p. 3, Asian-American scores on p. 15
I do agree with you that US schools are not cost effective - I've long been a proponent of cost cutting. In my view, the biggest problem we have with US schools is cost, not quality, and we should focus our efforts on making school cheaper.