hard time

Big boy had a hard time at school yesterday. He refused to finish his math paper and did really poorly on the math fluency test. I don't know if he doesn't know the answers or if the amount of problems was overwhelming to him. I told him he can't give up if something is hard to do. He has to keep at it. But how do I know when his senses are giving him problems?? Ugh! I wish I could just watch him at school for a few days. I bet my heart will break.