Cut him a little break. It's the end of the school year. Most kids check out several weeks before school ends.
At the same time, the teachers are also tired and looking forward to the end of the year. So, they don't have the same tolerance level that they had at the beginnig. Especially since they know he KNOWS the rules.
In our area, there's only three weeks of school left. (or two... I forget) So, I just tell my daughter "Just get through this week, it's almost summer". But, she's almost 18 years old, so it's easier.
I wouldn't take privelages away that have nothing to do with the actual crime. Perhaps you can set up something else instead?? Even if it's to add chores (which I know also have nothing to do with the crime either) But, if he gets a red card, maybe he could vacum the stairs, or clean the yard alone, or something tedious that he won't HATE, but he won't love either. Then, discuss it with him in advance, and set something up. If he does a good job at his chore, he'll also feel good about himself too.
I joined a fitness/weight loss challenge. We had to come up with a charity we'd like to donate to. I got three jars. Filled one with 52 marbles. Two were empty. Every day that I exercize, I put one marble in the charity jar. Every day that I don't, I put one marble in the other jar. At the end of the challenge, I have to give one dollar for every marble in the other jar to my teenager. Obviously, I don't want to do that. SHe keeps coming in here, looking in her jar and snickering. LOL So, I work really hard to keep from giving her my money.
Maybe you and your son could set something like that up for him. Put out three jars, put marbles for all the remaining school days in them. Each time he pulls a red card, he puts a marble in a jar for someone or something else. But, every time he stays on green, or even yellow, he can have a marble in his jar. Then, on the last day of school, maybe he can have money, or junk food or some kind of reward that equals his marbles in his jar. But, for every marble in the other jar someone else gets that reward instead.
Just throwing ideas out there for you.