The Together Tree by Aisha Saeed illustrated by LeUyen Pham

 Rumi is a new student. The other students do not protest when Asher, a bully, is mean to him. When Asher throws a rock, and it scrapes Rumi's knee, other students finally gather their courage and befriend Rumi. 

A didactic story  Based on the author's son experience

-Borrowed from the library.