I took as many AP classes as I could in high school, which was only 5. Unfortunately you are at the mercy of the classes your school/district offers. In underpriveleged neighborhoods I can imagine this would be very little.
I think my credits amounted to a little more than a semester's worth of college credits. However, to fulfill the degree requirements I still had to take the full 4 years. But the AP credits were helpful in allowing me to skip some of those GE requirements in favor of picking up a minor in Economics.
My high school offered two AP classes - AP US History and AP English something-or-other. I didn't take the latter one (hence not being clear on what the name was...), but I did take the former. I only received a 3 on the exam, though, which wasn't sufficient for credit at my first college.
Out of my class, though, that 3 was the second highest. One person got a 4, and everyone else who took the exam scored 2 or below.
The 3 definitely should have counted, that's unfortunate. And don't feel bad - the AP US History test is actually one of the harder ones. I "only" got a 3 and that was the highest score in my class, and I went to college to get a history degree! It was just a tough test.