charm school 
noun dated or humorous
An institution offering training in social graces such as etiquette: not all of the bar staff appear to have benefited from a stint at charm school...
- But he did manage himself like a charm school valedictorian.
- Dressing in my normal charm school uniform of a pleated skirt, white blouse, and black knee-highs, I joined Seth downstairs.
- Her sister was still in her last year of charm school, which Natasha had narrowly graduated from the year before.