Post #3 makes a compelling point regarding the advanced subjects now routinely taught in high schools in America. And post #4 makes a nice point about how the context of education is changing along with cultural shifts.
There is some disconnect between these two points and that, to me, is a good description of the education situation today. There is a confusion about how to measure success, which leads to obvious difficulties in creating opportunities to succeed.
With more and more people gaining college degrees today, the purpose of high school education (its goals, its necessity even) has been somewhat confused. Despite a growing insistence on "standards" and uniformity in classrooms at all grade levels, the idea of the Big Picture is not widely shared or widely understood, in my opinion.
This confusion can lead to a perception of decline in quality, but it seems to me that the decline comes down to a shaky sense of context for lower education, its purpose and its role in society.