Final answer:
August and his mom leave the school abruptly because August is being bullied, and his mom rescues him.
Step-by-step explanation:
The reason why August and his mom leave the school abruptly is because August is being bullied, and his mom rescues him. In the given text, it is mentioned that August was bullied in the 1st grade and that he stood up for himself. This implies that August's mom takes him out of the school to protect him from further bullying incidents.