Regarding the hilchos tsnius currently in print: There seems to be some confusion due to its level of kedusha.
Current trends have led to the publishing of these sefarim. However, Tznius is a multi-faceted thing. There are basic halachos that need to be kept (specific areas that are ervah). There are some variant determinations by rabbanim about the exact definitions of those areas. One needs to ask their Rav.
In addition, there is a whole other area, that is extremely dependent on the situation. This area requires sensitivity and judgement. Girls are supposed to be taught judgement. When people are given black and white rules about things that require thought, eventually it can backfire. Not only do they dismiss judgements that they don’t understand yet, they also can chas v’sholom come to dismiss the basic halacha R”L.
In plain english: they can get confused by yiddishkeit, chas v’sholom.
There are communities that deal with all issues by making more and more rules. Chasuna Takanos, Shidduchim Takanos, etc. For some people, this works. They know what to do, what is acceptable, and they do not have to make their own decisions. Hopefully the personal avodas H-Shem or Yiras Shamayim of these people will be enhanced.
However, there is a huge price paid by those who do need to think for themselves in order to effectively be ovdei h-Shem. They may quickly be labeled rebels, for not accepting these extra – sometimes arbitrary – rules. And once someone considers himself a rebel, nothing matters any more.
The rules of tznius have not changed, and the sensitivities and judgements that need to be learned, need to be taught in every generation. The “simple solutions”, where there is a “short list” of acceptable clothing… or a uniform… have short term gains, but long term losses. When a generation of frum girls seem to be clueless, it is apparent that the problem is not because there aren’t enough rules. It’s because they have stopped listening. Why?
In the zechus of the efforts of the many people who are trying so hard to restore kedusha to klal yisroel, may we be zoche to merit teshuva shelaima, bifrat u’bichlal.
zochreinu l’chaim, Melech chafetz b’chaim.