This [1] page offers a raw table with PISA, a standardized educational performance test, results across nations. We're now losing to places like Vietnam in Math/Science. This article mentions we spend about $11,000 per student on education. The per capita GDP of Vietnam is $2,305. Their per child spending is, in turn, going to likely be some fraction of that.
It's getting quite silly. This [2] is an interactive page allowing you to compare nations' performance based on OECD PISA scores across the world using a wide array of metrics - click on a country to get details and the ability to compare that country to others. The US problem is not with how much money schools get. It's not even with how much money teachers' get. You can find data on that here [3]. The problem is not money.
So what is the problem? I think that's why people like to just blame money, or the lack thereof. It's easy. Trying to figure out what the actual problem is is going to be extremely difficult. And as political correctness is such a hot trend in the US, some factors cannot even be considered which isn't exactly productive for trying to figure out the most effective solution.
[1] - http://www.businessinsider.com/pisa-worldwide-ranking-of-mat...
[2] - https://www.oecd.org/pisa/
[3] - https://data.oecd.org/eduresource/teachers-salaries.htm