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)?