Wow. I truly think this is a ridiculous post. Your child broke the classroom rules by coming unprepared for class SEVERAL times in ONE WEEK. It's not like he doesn't know he needs a pencil/notebook for class!!! The consequence for breaking this rule is clearly set out. Although you say you are not undermining the teacher's authority, that is EXACTLY what you are doing by refusing to accept the consequence that she has assigned for that misbehaviour.
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I disagree with this, for a couple of reasons.
1) Forgetting his notebook/pencil should have been ONE infraction. Especially since the teacher has been inconsistent in enforcing infractions all year. Little Billy forgot his book last week...no infraction. Joey forgets his notebook and pencil on the same day...two infractions???
2)There should not have been any infraction for leaving the book in the locker since the teacher had told them they would be working on something else for that class, and then changed her mind.
You say the "consequence for breaking this rule is clearly set out" however, it is not being consistently followed by the teacher. She can't expect parents to back her up when she is inconsistent and wishy washy with the punishments.