I went to an American private school when I was abroad and followed their "education plan", it was like I was put 3-4 years backwards to say elementary school level...
the "tests" are usually multiple choice answers and if you are not a complete moron you can pass US middle school with no studying at all...
I actually had trouble when I returned back to normal non-american schools because I had missed so much in math and physics that I had to start reading books again
I do not think americans are stupid nor that they have low IQ...we are all homo sapiens and its a bullshit argument...but the US education system is a joke...not commenting on yale or MIT or harvard , just your basic middle school in the USA...its like your health care, over priced and bullshit...