All of the lessons learned in Mayberry were certainly not learned at Mayberry Union High. Let's think about important lessons learned by Mayberry citizens:
Opie learned a valuable lesson about heedless actions when he killed the mother bird with his slingshot. By the time he had raised those babies and let them fly free he was a more mature young man.
Aunt Bee learned a hard lesson about bargain shopping when she forgot to consider things like taste, toughness, loyalty to her local butcher, and the condition of her freezer. She also learned that sometimes the best thing you can do is just call the man.
Barney learned not to tell Gomer anything about his relationship with Thelma Lou! The "hip pocket" remark did not go so well.
Howard learned that giving up the rat race and stress of the county title department, to go live on the beach, wasn't all it was cracked up to be.
(Life on the beach doesn't sound relaxing to me at all right now.)
One lesson ole Barn never did learn was that he was a really BAD singer. Never could understand that, though. That morning when he and Andy were harmonizing on "Lose All Their Guilty Stains" his voice was extra fine. Maybe his uvula or that oblongata-thing suffered an injury or strain and it was all downhill from there.
He did improve a bit however with the help of Miss Poultice. His "me theys" were definitely an improvement from his debut as first tenor singing good ol' 14A. Not quite as good as Leonard Blush though.
AND his breathing--WOW!! Eleanora could put a breathing lesson on a feller. I agree with you, Mayor. Barn couldn't hold a candle to L.B. I don't think Barney could have stood the stress of singing at the insecticide convention like Leonard did.