You are quite right about tanning. Tan skin use to be indicative of laborers who work in the fields. Well to do educated and privileged people didn't have to do this- so tan skin was a sign of the "lower-class". This is where the term "blue-blood" comes from- because aristocrats could maintain their fair skin showing their blue veins beneath.
And you are also right about various scholastic achievement tests peaking in the early '60s (hmmm- just when I graduated) and falling ever since. There have been a number of "adjustments" made over the years both in content and grading trying to keep the tests relevant to "current standards". It's a bit like if your diet isn't working- just recalibrate the scale to say what you want. Another term is "grade inflation"- where what use to be a "C" is now a "A". Some schools no longer give "F"s at all- because that would hurt the students "self-esteem". This "reward for nothing" even permeates school sports now- everyone on a team gets a trophy regardless of how poorly they played.
Anyone who thinks kid's education today is comparable to what we had need only look at any teen internet forum where nearly every post is filled with spelling and grammar errors.