Baltimore schools are well-funded. The cost per pupil is about $14,000 per year.
Beyond that, I'd suggest that the teachers are well-trained, motivated by good intentions and work hard. They'd have to have those characteristics in order to go to work every day in that environment.
Further, the American education industry, whatever its faults, isn't trying to screw up. In fact, it's constantly trying to improve. There is no doubt in my mind that American education techniques are, for the most part, superior to ones from 100 years ago or even 20 years ago. That's the nature of a skilled profession where a lot of work is put into improvement.
So if it's not money, it's not motivation and it's not incompetence, what is it?
Maybe if your kid can't read or do math, you need to do something about it.
I don't know about you, but I didn't have access to anything remotely like this when I was learning fractions for the first time. It looks like if you want to learn, there are lots and lots of ways to do it.