You can't really compare the school systems of a homogenous country with low income inequality to one where 30% of the population is from either a historically oppressed racial minority group or relatively recent immigrants. It's especially misleading to look at school systems in urban areas, because that's where the U.S. puts most of the poor people.
That is not to say we don't have a problem here in the U.S. But the problem isn't with the education system, it's with how we've dealt with the disadvantaged in our society.
A great example of this is Chicago. Finland spends about $10,000 per year per student. Chicago spends about $20,000 per student. Chicago teachers are paid over $70k/year on average, almost double the $37k/year Finnish teachers are paid. Why does Chicago do so poorly? It doesn't take a genius to figure out that it has nothing to do with money or school quality, but the fact that 86% of Chicago's students come from low-income families, and 87% are disadvantaged ethnic minorities.