LifeCycle Events: Marriage and Sexuality: Modesty for Little Girls:
At what age do girls have to begin dressing according to the Jewish laws of modesty?
From the age of 3, a girl should dress in a modest manner appropriate
to her age in her society. This is very relative. In America it might
mean that she can wear short sleeves and pants; in Meah Shearim it might
mean that she must wear sleeve down to her wrists and tights.
>From the time that she is considered a "young lady", as opposed to a
"little girl", she should dress in the modest manner prescribed by
Halachah: sleeves covering her elbows, and dresses or skirts past her
knees. Generally, by age six or seven a girl is in this category.