Modesty norms

Hello B.
First, welcome and long live independence.
Secondly, it seems to me that the “stream” is definitely a measure of what a reasonable and appropriate norm is. Therefore, it is not about swimming with the stream, but rather that the stream is part of the correct measure itself. This is in contrast to other questions in which even if the stream thinks X, you can think and act Y. Modesty is something determined, among other things, by the stream. But even beyond the laws of modesty, one must also consider the system in which one is located. If an educational institution sets dress codes, they must be taken into account even if you think that these are not the correct boundaries of modesty. Overall, you are not alone in the world and your actions and appearance also affect others. Just as on the road, I do not just drive however I please, because even if I can determine and take risks for myself, my actions also endanger others. Although if there is a fatal injury to the individual, he does not always have to consider the environment, this is usually not the case.
I think it is possible to explain to children (at least from a certain age) that there are reasonable norms of modesty, even if we do not have precise measures to determine them. God expects us to behave appropriately. For example, the Torah commands, “Do what is right and good,” but nowhere does it define what is right and good (and of course there are arguments in various situations about what is right and good). It probably trusts us to understand on our own according to our common sense. And even if there are arguments between people, because common sense is not mathematics, and perhaps there are even several correct answers, a person should behave as he understands. This is the very expectation of the Torah from us.
An example of this is the search for a correct socio-economic system according to the Torah. In my opinion, such a search is wrong, since the Torah only expects us to act in a moral, just and proper manner. If you are a socialist, then the Torah wants you to act this way, and if you are a capitalist, then the Torah wants you to act this way. I was a boy and I have grown old, and I have not seen anyone who was a socialist himself and because of what he found in the Torah became a capitalist, or vice versa. Everyone plants his de facto values ​​in the Torah, and then one has the feeling that he found guidance for his view in the Torah. So why do this at all?! Just do what you think, without raping the Torah for it. Of course, if there is a specific command against what you think, you should comply with it, but when there is none, then there is none. This does not mean that this is a neutral area that is not important to the Torah. There is a will of the Torah here, but since these are complicated problems that depend on society, norms, and the socio-economic situation, it did not set specific requirements. In such situations, the Torah’s will is that we act according to our understanding (the true one, not our creation).

On the sidelines. Life in a non-Haredi system is difficult, among other things, because of this. The Haredi system tries to embed all customs and norms in the binding and uniform halacha. Although this is not true, it is of course easier educationally. In the non-Haredi (or Haredi) system, the situation is different, and this raises educational difficulties. But since you have chosen this direction, I think there is no choice but to confront it head-on and explain to you and your children that this is the situation. We need to internalize that the will of the Torah is not always expressed in uniform and rigid norms, and this still does not exempt us from seeking what is right and what is right for us in our situation (and also to consider the environment, as mentioned). The weight of “and you shall do what is right and good” in such a system is much more significant than in the Haredi system.
Good luck,