Don't know about the "prep" look but penny loafers are a sure sign of the 80s!
I remember at the high school I worked at, we had an 80s day.
I had a to-the-knee blue jean skirt that I splashed bleach all over and then fringed the edges.
Black tights that I cut little holes in.
Crimped my hair...looked REALLY big.
Hooped earrings and bangle braclets.
Took an oversized sweat shirt, cut off the sleeves and took out the neckline. Wore a tank under that and had it half hanging off my shoulders.
Oh, don't forget, they also wore scrunched down socks with their heals!
...or was that the early 90s?