The first few thoughts that came to my mind are...
1. He is bored with revisiting the information
2. Lack of stimulation due to this
I will give you my thoughts as to why... My friend has a son who has autism ( am not saying your son does but the SPD is a common factor) he is in regular gen ed classes. He stays for the instruction and leaves to go do his work in another room. He cannot understand why there is the need for all the other "nonsense" he is very literal and straight forward thinker. You do what you are supposed to and get it done that is it. My son is very literal too. he is 8 with SPD. He sometimes can't understand why there is silliness as well.
Or by Thursday he is too overwhelmed and he is shutting down. If he does not have any pullouts during the day like for OT, Speech, Social worker or for her to even allow him to walk a note down to the office even if it doesn't say anything . He might need something ot light a fire under him. If she is not understanding then you should seek to have him placed in a another class with a teacher that does understand his needs. Or you can get him a sit fit cushion that will give hi constant motion to keep him alert. Tell her you want to sit on the class on Monday and observe then also on Thursday. Then you can see the difference as to what is going on and to his behaviors. If she is not going to try and solve the problem then you do it and take notes get all the ammo you can so the school has to listen. The weekend does help with getting out all that energy which makes it easier for them to focus on a task. He could be shutting down by the end of the week because he has just had it! My son is a sensory seeker and very impulsive so he has huge impulse issues when he get frustrated he acts out. He too is highly intelligent and I believe gets bored as well. He gets pulled out during the day, he eats lunch in a separate room because of all the noise in the cafeteria, so he has tools to help him cope. This teacher needs to work with you to make his day successful. I would go and observe, or try on Thursday before you go to school to have him to an energetic activity like running or playing some physical activity to see if that makes a difference in his day. I hope this made sense I feel like I was going in circles lol.