Ah... okay. I tend to think in terms of STEM (math in particular, since I'm a math tutor), so the humanities are a whole different beast. I don't have too much of a frame of reference for humanities areas. I agree, though, that there's not enough of an expectation to "think" in high school and that college encourages "original" thoughts whereas high school tends to "impose" ideas on students. I went to a pretty decent high school, and even in my senior year I had a teacher who literally gave us our thesis for our essays. Too much hand-holding, not enough thinking. To be fair, it was a non-honors class, but everyone in our class was college bound. I had been in honors classes previous years and wanted a break, but I didn't think the spoon-feeding would be that ridiculous.
Sounds like your high school was very middle of the road. In the two districts I am speaking of, the median income of families in the district with the "better" public high school is more than $100,000 more than the median income in the low-quality district (I just looked it up, so I know for certain that the disparity is this big). These two districts are only a short drive away, too.
The major problem is socioeconomic-- parental income is the number one predictor of educational outcomes. In a district where all the students come in behind due to the lack of exposure to enriching activities in childhood, the teachers are forced to lower from day one (can't get a child to read until they know their ABC's).
I talk to students from both these districts, and it does seem that the wealthy district does a damn good job of preparing kids to "think." I went to school in a wealthy district, but it wasn't as wealthy as the district I speak of and education wasn't seen as important in my district (the ethnic/cultural makeup of my town is different from that of the wealthy district I speak of above), so there was no pressure to get into the ivy league or win academic competitions or accomplish "extraordinary" things in my town. Your town was probably more like mine, in that it was more about "going through the motions" and doing just well enough that you'll be able to succeed later in life (rather than being about making it to the "top").
My district was also different than yours in that graduation rates were 100% and college attendance was 99%. This meant a good number of our graduates were unprepared for college by virtue of the fact that they were the bottom of the class. Still, our high school was good enough that most of these weaker students chose easy majors and managed to make it through college, too. Others made it part-way through and are "still working on it," but a college degree is pretty much mandatory here and very common to have (not at all so in the lower income district).