Is it permissible for a woman to go to the market to take care of her needs or to her children's school, and is there a specific time for that?

It is permissible for a woman to go out to fulfill her needs, by day or by night, provided that there is no risk of fitna (temptation/strife) and that she adheres to the etiquette of Islamic law. However, if she is married, she may not go out except with her husband's permission and only out of necessity. The madhahib (schools of thought) differ regarding the exit of a woman who is in her revocable iddah (waiting period after a revocable divorce). The Hanafis and Shafi'is prohibit her from going out by night or by day, while the Malikis and Hanbalis permit her to go out by day to fulfill her needs, but she must stay in her home at night. As for a woman in her iddah after an irrevocable divorce, the Hanafis prohibit her from going out by night or by day, whereas the Malikis, Shafi'is, and Hanbalis permit her to go out by day for a need, but prohibit her from spending the night outside her home, except out of necessity.