Well without knowing the details of what precisely your son is finding frustrating, I *can* tell you that level B is designed as an entry-level course.

To my understanding, it's not even so much that B is a full review of A... it's more like B was the "original" entry into the program, and later they made A for younger kids.

So assuming that your son is ready for level B, then no he won't miss anything by skipping to B.

Otherwise, you can certainly combine and skim through lessons in A if they're really way too easy for him. I do think it's important to touch on everything, since so much of it is setting up concepts to be further developed later, and much of it is a different approach than what most kids have absorbed until this point through educational tv or whatever. But you don't have to spend as much time doing repetitions and games etc if they obviously understand it already.

So if you decide to stay in A, I wouldn't SKIP anything, but just reduce repetition. And I would even tell my child what I'm doing -- "I know this stuff is easy for you right now, but we do have to go through the basics to make sure we're not missing anything before we go on to the tougher stuff. Just bear with me and play along for now, we'll get through this part as quickly as we can, and I promise you that we'll soon get to the fun stuff and it will alllll be worth it."

Often times, it's just the need to feel that they've been heard and respected that makes all the difference. If they know you understand, they will often be more patient. :)

Another option, of course, if he REALLY does not like math (ie, if it's deeper than just that it's "too easy"), you can just skip it altogether for now. He's only 5, there's lots of time to catch up later. In truth, most math up until about grade 3 is really just dumbed-down baby steps so that you can say your kids are "doing something", but every year it repeats everything and only adds a little bit...it's usually VERY early to just start at age 7 or 8 or 9... or 10... heh... when their brains are better developed and ready to tackle the tougher stuff, and just go from there.

I think the RS approach is better than the typical math programs because it really is NOT just dumbed-down baby-step stuff, there really is important concept building going on. But if they're really not into it, they won't really be any worse off if you just start them later -- maybe even starting with level C (going through Transitions first) if they're older.