シック

今夜どこか行くの？シックに決めてるじゃない。

Going somewhere tonight? Look at you - all dressed up like that.

シックで上品(じょうひん)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。

It's said to be a girls' high school characterised by its quiet and traditional feel and a chic, high-class uniform.