Is it permissible for a teacher to eat with his students from the money allocated for their feeding, knowing that they live and eat in the same place?

The answer to this issue depends on the intention of the donating entity. If the teacher is included in the grant, then he has a right to the money, just like the other students. However, if the grant is designated for students only, then the teacher has no right to it; rather, he is an agent distributing it according to the donor's condition. The teacher should inquire with the donating entity to dispel any doubt.