I would say they have seriously been going downhill since the early 80's. That's when I first hear the term "dumbing down" of our public schools.
That may have been when we first started to hear the term "dumbing down", but it started long before that. Our schools used to require a lot. Back in the days of our founding fathers to graduate from high school required a person to be able to communicate in multiple languages so they could read the classics of literature in the original languages. Most of them could read, speak, and write fluently in Greek, Latin, French, and German. Some could also do the same in Hebrew for they made Bible study a big part of their lives.
And on the subject of economics we, as a country, have been woefully ignorant of the subject for well over 100 years. Keynesian economics started being taught in college back in the 1930s, and Keynesian economics is nothing but a con game. It ignores the foundational economic laws that are required to understand how an economy really works, what money actually is, and replaces that knowledge with economic theories discredited long before Keynes published his book, General Theory. We have also been kept ignorant of our founding father's ideas and motives for a long, long time. This was happening during the days of Abraham Lincoln for Stephen Douglas wouldn't have even dared to use all the fallacies he did in his political speeches if the public had known the truth. It's why Douglas' political power and influence began declining after Lincoln tore him to shreds in their debates by exposing his deceit and revealing what the founding fathers actually stood for regarding slavery.
As for you and I, we haven't lived in a truly free society with a free market during our lifetime. The last of the truly free market went by the wayside when the FED was created, and when that happened our liberties began disappearing at a rapid rate. Think about government spending which steals from us through taxes and inflation and reduces our liberty. Deficit spending began to really escalate to being an every year event clear back in the 1890s when the income tax was created for our constitution did not allow the federal government to tax us directly. Both parties collaborated on that because of their desire to spend for spending on their part buys votes and keeps them in power as long as the general public is economically ignorant enough to not understand that deficit spending, and the resulting increases in taxation, steals wealth from your pockets and mine. We the people get hurt the worst by both because the banks just skim the profit off the top through interest on loans, both public and private. And government spending is guaranteed to be paid. By who? We the people.
It's like what Alexis de Toqueville said about our form of government. It would last until our politicians figured out they could buy votes with the public's money. After that it was all over but the weeping. And the politicians have been buying votes now with our money for over 100 years.