What is the ruling on looking at women out of the corner of one's eye with the intention of focusing on something else, such as the teacher or the whiteboard, when a part of one's gaze falls upon them because they are in front, or when looking at the teacher's face, the corner of one's eye unintentionally falls upon the rest of her body?

There is no difference in the ruling on looking at women, whether one looks with the corner of the eye or the center of the eye. The gaze is one and forbidden. The Prophet, peace and blessings be upon him, said: "Do not follow a glance with another glance, for you are allowed the first, but not the second." Looking with the corner of the eye is a form of furtive glancing, which is how Mujahid interpreted the words of Allah Almighty: "He knows the treachery of the eyes and what the chests conceal," meaning furtive glances at what is not permissible. However, if the intention is to see a phantom or image of women alongside something else without intending to look at them, then one is not held accountable for that.