I believe the issue with Tznius amongst today’s youth and adult alike, stems from a more fundamental issue, that people have lost the appreciation as to the point of Tznius, and have lost sight of why living B’Derech Hashem is so important.
Educators and parents nowadays explain away Tznius with reasons such as so as not to be too attractive to the men, or not to be too haughty or involved in your image. Although these are valid points, but they can easily be disregarded legitimately with arguments and perhaps rationalizations.
The Mechanchim should spend time focusing on and stressing the power of the female body and its preciousness, and the power it gives a woman if she wields its power and keeps it special and refined. In the same way a person does not flaunt his precious diamonds in the street, or invite random people off the street into their home, and certainly not the bedrooms, and certainly not the master bathroom, because all of these things would diminish the inherent personal value of the object owned.. The home or the diamond only costs a set monetary price, but the female body is priceless and infinitely more powerful than money. If a woman realizes this deeply and recognizes the power she has by keeping her most valuable possession to herself, there is no doubt that she will instinctively dress in a more refined, Tzniusdik fashion, the degree of which will only increase as time goes on, and the struggle will only become smaller.