“The time to educate is when kids are young. I think telling a 16 year old that her mode of dress is unacceptable (when she attends a school where her peers are doing it or is exposed to it firsthand) is a recipe for rebellion. Teenagers are first recognizing their own beauty and begin to equate self worth with it. They don’t see where their choices will lead and how it can spiral out of control. ”
Mommamia is right. When I was about 14-15, I was going through a rebellious phase and the clothing I wore was not tznius. My father told me numerous times that the clothes I was wearing was too short, too tight… It only made me worse.
After a while, my father began to realize that it wasn’t helping, so he gave me his credit card and told me that for every shirt/dress/skirt I threw out, I could buy 2 more. So I emptied half my closet and went shopping 🙂 It was that that helped, not the mussar.
So I guess that if the mussar is given in the right way, in a way that will help (in my case, a shopping spree) then it might be okay for a father to do it. I still think that relaying the importance and beauty of tznius is primarily a mothers job. (Me and my mother didn’t get along back then so she was not the person to give me tochacha.)