Is it permissible for a girl who wears the khimar to stipulate to her guardian that she will wear the niqab after marriage and stay at home to raise her children, even though she knows that she goes to school and the teachers do not want her to attend with her face covered?

Concealing a woman's face from foreign men is obligatory according to the most preponderant view among scholars when there is a fear of fitna (temptation/strife). This is the view of the majority of scholars from the four madhhabs. Enduring hardship in adhering to religious obligations is a great jihad. Disbelievers do not differentiate between full hijab (definition) or head covering; all of it is considered unusual by them. It is necessary to be patient, steadfast, and adhere to religion and what pleases Allah. Delaying the covering of the face is not permissible except in cases of urgent necessity, such as essential study in a country that does not permit face covering. In such a situation, it is permissible to temporarily adopt the view that covering the face is not obligatory. When the necessity ceases, or it becomes possible to leave that country, one must promptly resume covering the face.