シックで上品な制服と歴史ある静かな雰囲気が特徴の女子高なのだという。

。

Apparently it's a girls' high school known for its chic, refined uniforms and a quiet, historied atmosphere.

Literal

Chic [and-で] refined [attr-な] uniform [and-と] history-having quiet [attr-な] atmosphere [subject-が] characteristic [gen-の] girls-school is-[hearsay-という].

シック is the loan 'chic' (French via English). 歴史ある is a contracted form of 歴史のある ('having history') — の often dropped when used attributively. The overall noun-phrase structure is [A]と[B]が特徴の[C]: 'C whose characteristic is A and B.' 女子高 ('girls' high school') is a compound. なのだという at the end is a formal hearsay structure: explanatory なのだ + という ('it is said that'), giving the sentence a distanced, reported feel.