"Harper Valley PTA" is a country song written by Tom T. Hall that was a major international hit single for country singer Jeannie C. Riley in 1968. Riley's record sold over six million copies as a single. The song made Riley the first woman to top both the Billboard Hot 100 and the U.S. Hot Country Singles charts with the same song, a feat that would go unrepeated until Dolly Parton's "9 to 5" in 1981.

The song tells the story of Mrs. Johnson, a widowed mother of a teenage girl, who becomes outraged when one afternoon her daughter brings home a note from her junior high school's PTA decrying Mrs. Johnson's supposedly scandalous behavior by small-town standards. According to the PTA she is setting a bad example for her daughter. In response, Mrs. Johnson attends the next PTA meeting (being held that same afternoon), wearing a miniskirt, to the surprise of the PTA members. She then exposes various episodes of misbehavior and indiscretion on the part of several members of the PTA, concluding with, "This is just a little Peyton Place / And you're all Harper Valley hypocrites!"

The song makes two references to short hemlines ("you've been wearing your dresses way too high"; "wore her miniskirt into the room") in reference to the miniskirt and the minidress, which had been gaining popularity in the four years since they were first introduced.

The expression, "This is just a little Peyton Place..." is a reference to the television show based on the earlier novel and film of the same name wherein a small town hides scandal and moral hypocrisy behind a tranquil facade. The show, then in the top 20 of Nielsen ratings, was in its fourth season when "Harper Valley PTA" was released.

...
Wikipedia