Probably a good approach would be to clone the teachers over the other photo. But one student will still remain affected.
Mask the faces on the second photo, copy > and paste on the first image.
Here is a rough test.
And here is a surreal image of the objects. It is a simple matter of masking coping pasting and adjusting the curves to match the luminosity.
The poor kid on the left needs an additional makeup.
If you had not the other photo it would be almost impossible to heal the image.
Take this as an experience, when you are taking a group shoot you are the commander. So look around, look at the environment, the people, the best spot stand, and turn off the projector!