Without knowing exactly what's frustrating him, and how he's expressing that frustration in class, it's difficult for me to respond very specifically. However, I have a DS6 who goes to 2nd grade for Everyday Math (my DS6 is in 1st grade), and I can tell you about our experience. First though, that's fantastic that they were willing to let your DS go up two grades in EDM. It can be difficult to transition into that curriculum without getting the base "language" of EDM in 1st grade and K. Regardless of whether he knows advanced math concepts, making sense of EDM is not terribly easy when you're thrown into it in the middle.
Regarding our experience as it may be relevant to yours, my DS6 is very proud to go up a grade with the 2nd graders, but he is also more reluctant to speak up in class to provide answers, or to ask questions, because of the age difference. My DS is not low on self-confidence, although he is more of an observer, and it's surprised me a little that he's as reluctant as he is in math. Thankfully, he understands the teacher and doesn't need to ask many questions, but if he were being particularly challenged, we would have a hard time with it because he wouldn't speak up to ask questions. His writing skills are also not at a 2nd grade level, which makes it difficult for him to complete work in the classroom sometimes.
I imagine this scenario might be multiplied for your DS, since your he's going up two grades, not one. The EDM curriculum itself can also be frustrating for kids who want to move along quickly, as others have noted, because EDM is extremely repetitive, and remains so from year to year, as it's a "spiraling" curriculum, meaning they revisit the same topics in more depth each year.
I don't know if any of this is helpful, but thought I would share in case it is. I think Grinity's response is great too.
