When you tell a girl what to wear (or force her to cover up with an oversized T-shirt), you control her body. When you control a girl’s body—even if it is ostensibly for her ‘own good’—you take away her agency. You tell her that her body is not her own.
When you deem a girl’s dress ‘inappropriate’ you’re also telling her, ‘Because your body may distract boys, your body is inappropriate. Cover it up.’  You recontextualize her body; she now exists through the male gaze.  What do dress codes say about girls’ bodies? By Marinda Valenti