What is the age at which a woman should observe hijab in front of a boy?
Question

                What is the age at which a woman should observe hijab from a boy – is it when he reaches the age of discernment or when he reaches the age of puberty?.
Praise be to Allah.Allaah says in the passage 
    where He speaks of those to whom it is permissible to show one’s adornments 
    (interpretation of the meaning): 
“…or small children who 
    have no sense of feminine sex”
[al-Noor 24:31]
If a child shows some 
    awareness of a woman’s ‘awrah and starts to look at her and talk to her a 
    great deal, then it is not permissible for a woman to uncover in front of 
    him. 
This varies from one boy to 
    another in terms of natural disposition and in terms of the company that he 
    keeps. A boy may have a greater interest in women if he sits with people who 
    talk about them a great deal, and if it were not for that he would not be 
    particularly interested in them.  
What matters is that Allaah 
    has set the guidelines for this matter when He said (interpretation of the 
    meaning): 
“…or small children who 
    have no sense of feminine sex”
[al-Noor 24:31]
i.e., these are among the 
    ones in front of whom it is permissible for a woman to show her adornments, 
    if they have no interest in women. 
Shaykh Ibn ‘Uthaymeen 
    (may Allaah have mercy on him), Majmoo’at As’ilah tahumm al-Usrah 
    al-Muslimah, p. 148

    Among the things which indicate that a child has started to 
    be aware of a woman’s ‘awrah are the following:

    -He describes women to others

    -He can distinguish between a 
    beautiful woman and an ugly one

    -He compares the way women look

    -He stares at women for a long 
    time 
Undoubtedly movies and soap operas, as well as social corruption, lead to children being aware of women’s ‘awrahs at an early age, so we have to be very careful.  We ask Allaah to keep us safe and sound.