The medication might also help him develop strategies to manage the anxiety better too...

Maybe if the school makes the more challenging work a 'special project' for if he wants to... or he can choose from some activities - some at the level he is capable, and others at a harder level.... then he will feel more in control of what he can do....

maybe the psych can come and meet with the teachers and advise them directly???

I do hope it goes well for him, I agree with doubletrouble - the earlier you put things in place to help, the more likely he will learn to manage.