While I dislike to concept of modest and therefore immodest (though I don’t have an issue with “appropriate for the occasion”), the reason there is no modest section for men, @Ifpicklesweretickles, is because men aren’t groomed from infancy to think that the more flesh they display the better. Little boys’ clothes ranges don’t include, for example, tiny shorts, tight firing T shirts with cap sleeves and crop tops. All of which are completely impractical for young children aside from anything else, though I suppose it works out well for the purveyors of sun cream - gotta turn girls into consumers as early as possible!
So we need to ask ourselves why the western world is so keen for little girls to display flesh in a way they aren’t keen on little boys doing the same.
And you need to bear that in mind when you rail against schools not liking girls turning their skirts into belts.
This is not equality. It is not liberation from the patriarchy.