I have both SCM books and MUS. I don’t foresee a problem with her switching. If she finishes SCM book 2, she would definitely be ready for Gamma but would actually be ahead since would have finished times tables to 6. She should could just skip ahead to the appropriate place. Gamma covers multiplication tables in depth. It also covers perimeter and area. Each MUS level focuses on one specific concept but also adds additional concepts where pertinent. From my own comparison between the two, the additional concepts covered are not difficult to add in. She really wouldn’t have missed much from Alpha and Beta since those focus on addition/subtraction facts. The only extra things I can think of would be simple things such as tally marks or comparisons (greater than/less than).

I did take a quick flip through Beta and yes, you’re right, those topics are covered (they’re kind of “side” topics, with the focus being on addition and subtraction). Personally, I wouldn’t worry too much about that because I feel that those are best covered through real-life exposure. My kids learned how to tell time using an actual clock (especially once they could count by fives). We refer to our outdoor thermometer often and use things like paper sloyd to gain practice with measurements and using a ruler (that’s really all that Beta does…have the child measure lines in the workbook). But you know your child best. I still don’t think she would be behind at all in Gamma, but that’s just my personal opinion.