Is it permissible for teachers to take biscuits specifically designated for students, especially when there are no students present to distribute them to?

Meals in excess of the students' needs should be returned to the authority responsible for them. It is not permissible for teachers to benefit from these meals unless they have permission from that authority or if it is customary for them to benefit from them. If it is impossible to return the meals, and this would lead to their spoilage or disposal, then it is permissible for teachers to benefit from them.