excuses of a poet

Poetry assignment requires the child write 10 peoms. This is classwork done over a period of time. By the end of the quarter, my 5th grader submitted 4 peoms. Teacher is disappointed and asks why this happened, to which he just shrugs. So, the teacher sends me an email and I ask my son why he did not respond to the teacher.
He just shrugs. By then I am frustrated also trying to delve into the root of the problem.
I then say to him "you should have some excuse.. you ran out of time or.. a writer's block..."
He: "yeah, I ran out of time, ok?"
Me:"Understood! if you gave me that excuse after doing 9 or 9.5 poems, great! not with just 4!"
He: Mmm. how about a "poet's block?" Will you accept that?
I gave up! go figure!