I lived in Aberdeen in the mid-80s, and "Sloan Rangers" were all the rage (mostly as the brunt of more working-class jibes and taunts). Preppy is very similar. Very upper-crust. Martha's Vineyard. Pink trousers with little green whales. Tartans. Private (aka Public) schools. Girls named Muffy. Boys named Biff. Eton. Exeter. That sort of thing.
I wouldn't call this a jumpsuit (those are full length and, well, a bit sexier, LOL).
I'd call it a culotte dress and/or a split-skirt dress.