Hmmm, it is important to learn when not to talk. And during an English essay (test?), it would be especially important to be quiet - as talking (even to himself) may well distract the other students around him (and lower their score!). 13 seems old enough to have learned this lesson. To receive a zero on the essay for talking seems excessive - unless the teacher had warned him about not talking during essays/tests in the past. The teacher's comment afterwards "Mr Zero" - it depends a lot on tone - it could be a friendly, though perhaps inappropriate, joke or an insult. Are you confident your son tells the whole story (in particular on whether this teacher has warned him about talking in class before)?
This is what I wondered as well.
Being parent to another 13yo, I mean-- I am amazed sometimes at the relevant information that she can overlook/omit in relating interpersonal interactions. Some of this is adolescent thinking, I'm afraid.
