While some private schools might have strict dress code policies resulting in disciplinary action (like detention or suspension for violating rules), physical assault is absolutely unacceptable and illegal. Any instance of this happening would be a severe breach of conduct, possibly involving criminal charges and civil lawsuits.
If you or someone you know experienced something like this, it's crucial to report it immediately to school authorities, parents/guardians, and potentially the police. This is not a normal consequence of any school disciplinary process.