How does a photographer need to adjust the focal length of the camera to take pictures of all the students?

If all the students on both sides don't take pictures, that is, everyone's image will become smaller and the object distance will become larger, that is, the distance between the camera and the subject will become larger. So the camera should be far away from the subject.

The greater the object distance, the smaller the image distance, so at the same time, the image distance should also be reduced, that is, the lens shrinks backwards.

So the answer is: stay away;