It's not hard to find examples of widespread ignorance in recent years. For example, in 2001 the Gallup Poll asked "What are the first 10 Amendments to the Constitution called?" 57% said the Bill of Rights, 6% gave an incorrect answer, and 37% said they didn't know. When Gallup asked the same question back in the good old days (more specifically, in 1954), 33% said the Bill of Rights, 2% gave an incorrect answer, and 65% said they didn't know. Knowledge didn't decline between 1954 and 2001--it increased.
What about those civics courses students had to take in order to graduate? At the time, many people didn't graduate from, or even attend, high school. In the 1954 sample, about 32% had an 8th grade education or less and 24% had attended high school but not graduated. That is, only a minority were high school graduates. The percent giving the correct answer by educational level:
HS or less 27% 38%
Some College 60% 61%
College graduate 74% 78%
The 2001 report didn't give a more detailed breakdown of education, but in 1954 46% of people who had graduated from high school and had no college got it right. So within each educational level, there was little or no change between 1954 and 2001. Regardless of what people study in school, more educated people are more likely to follow the news, which means they are more likely to pick up new information and less likely to forget the things they once knew.
[Data from the Roper Center for Public Opinion Research]