The principal of an elementary has taken away all recesses. the children in this school have begun to act out quite a bit, especially in the late afternoon. what is their challenging behavior probably saying to this principal?

Recesses, especially for the elementary students, are to time for them to take breaks and eat their snacks to make them last within a certain duration without having to deal with empty stomachs. During the late afternoon, the duration from lunch was already very long. This would make students go hungry and further, out of focus. 

The challenging behavior would strongly suggest the principal to bring back the recesses. If not all then, maybe only that on the afternoon.