Carnage (2011)

After an argument, 11-year-old Zachary punches his classmate Ethan in the face. Ethan's parents invite Zachary's parents to their apartment to address the matter in a civilized manner, but the conversation begins to escalate and the initial politeness dissolves. The constant phone calls, alcohol, and differences of opinion turn a simple discussion about the children into an intense struggle to defend them, revealing the true character of the adults involved.