Is it permissible for a niqabi teacher to uncover her face in front of male and female students in the sixth grade of primary school?

If the children are young and do not understand matters related to women, it is permissible to uncover the face in front of them. However, if they are adolescents, a woman must observe hijab (definition) in front of them and not uncover her face, due to the Almighty's saying: "Or children who are not yet aware of the private aspects of women." Ibn Kathir, Ibn Qudamah, Al-Kasanī, and An-Nawawi interpreted this to mean a child who does not comprehend the circumstances and private aspects of women, and cannot distinguish between a beautiful woman and a plain one.