Sigh. Just looked at DS's science test on physical vs chemical changes. There were 15 questions, he had 5 marked as incorrect. Here is the first:

Intro: Read about each physical or chemical change in matter. Answer each question.
1. You crumple a paper bag into a ball.
What change happened? DS answered physical. INCORRECT
Is the bag still a bag? YES
Is this a physical or chemical change? DS answered physical. CORRECT

Why is the first answer incorrect and the third correct? Because he was supposed to infer, apparently, what the teacher meant to ask (describe what the paper bag looks like now, or something like that) rather than what she actually asked, which he correctly answered. He missed two more for exactly the same reasons.
It gets better. The other two he missed had to do with the second question in the series, like this.
A metal toy is left in a puddle of water and it rusts.
Is the metal still a metal? He said yes. INCORRECT
Is this a physical or a chemical change? He said chemical. CORRECT
So he knows that rusting is a chemical change, but (and I haven't had the energy to ask him about this yet) my guess is that he answered yes to the other question because he is picturing a toy that has not completely turned to rust and therefore the metal part that remains is still metal. I find the question as written to be rather nonsensical and confusing.

Now I am again in a dilemma about whether to discuss this with the teacher or not. It is 3rd grade so I am not overly concerned about the grade itself, but I AM concerned about how DS is supposed to figure out when he is answering questions correctly or incorrectly when it appears to be quite arbitrary in many instances.