We moved over to Math Mammoth light blue. They don't have a kindergarten program available, but they did have a grade one. We started there, from the beginning, because I was genuinely that concerned about Mad Natter's retention. Probably didn't have to, but it helped. There was no more screaming and no more fighting over math, the days of tiles and beads chucked around the room (look - it's a CAR!!!) were over. I can't explain how much a relief that was.
Math Mammoth is extremely akin to Right Start, the primary difference is the time spent with manipulatives. You can add them in if you like, or leave them out, it makes little difference. The concepts thus far (and we're seven of eight chapters deep in Light Blue 1 at this point) have been easier for him to grok, and even better, he's been retaining them. He carries forward knowledge and uses it to help in the following sections, despite being exactly no better about review than he was before. Now, make no mistake, this program isn't going to end our mathy woes, as it still requires some work being shown (or, in our case, explained - because I scribe) and that is the bane of Mad Natter's existence. He wants to sit down, scrawl numbers on the page, and be done. He doesn't like that he has to tell me what he's thinking, why, and how he got to his answers. I strongly suspect there won't be any math program that will help with that.
Anyway. We picked up Math Mammoth Light Blue Level 1A+1B for $37.50. For both. Already I'm impressed, as we spent over $100 on each level of Right Start, so saving $60+ each year sounds like a wonderful plan. Once gotten, I printed out both levels, and dropped them straight into binders. I think once we're out of grade 1, I might just start giving Mad Natter the binders, rather than pulling the pages out and having to reorganize each day, but that's something for another day. They fit, albeit tightly, into two 1/2" binders, and went straight to the shelves, labeled. Mad Natter does between one and three pages daily, depending on how much of the pages are review, how much are new learning, and how difficult it seems to be. It is incredibly easy to adapt, being that I'm sitting right there, and he usually only does about half the problems on any given page. If he's struggling, we do more, if he's flying through, we do less.
The concepts and expectations are laid out clearly in each section, and multiple example problems are given. There are chapter tests included with the purchase, as well as a worksheet maker that will allow you to use the chapter tests as a basis to make up your own pre and post tests if you are so inclined. I often look at the contents of the chapter and make the executive decision to create a mock-up test to give to Mad Natter. If he passes it with a 90% or higher, we skip the chapter. If he passes with a 75% or higher, we remediate the areas he had trouble with, and then move on. It saves me no end of headache.
Also worth noting, Math Mammoth is often available via Homeschool Buyers' Co-Op. I do believe the last sale saw the 1A-6B books all bundled together for $75. Can't really beat that. All in all, we're happy with the program, and it's one that I wouldn't hesitate to recommend to anyone looking for a maths program.