Jen, I recently did a review of MUS for a local homeschooling friend who was looking at MUS vs. Saxon. Here was that review from my perspective...
We've been using MUS nearly 2 years at multiple levels and love it!
Yes, Saxon and MUS are different in their approach. MUS takes a mastery approach in that your student really shouldn't move on until they've mastered the concept. Saxon is considered a spiral approach, where they introduce a topic, then keep spiraling back to build on it. I have Saxon and we've tried it at the older levels for periods of time, but never completely through any grade level. I've spent much time looking at the younger levels and they look good, but very teacher intensive. Once you get on to MUS, there is very little prep.
Here's the intended way of teaching MUS...
There is a DVD, where creator Steve Demme teaches the new concept at the beginning of the lesson to the parent, these are approx. 5 minute segments. Then the parent teaches the lesson to their student. Then there are 3 practice pages for the student and 3 review pages for the student (use 1 per day as needed). If the student gets it, there is no need to complete all 3 practice pages, unless you have an OCD child like me who can't leave any blank workbook pages ;-) Once the child masters the lesson and completes the review, there is a test. Then you move on to the next lesson. All the levels we've done so far have 30 lessons.
I am currently homeschooling 3 kids at 3 levels and find it very managable. Here's how I teach MUS....
Ruben (K-1st - Primer) - each day he completes workbook pages with my guidance
RileyAnn (2nd - Beta) - Day 1 she and I watch the DVD together, then I watch her do a few problems to make sure she gets it Day 2 & 3 she completes practice pages typically on her own (she's my OCD girl and can't get enough workbooks) Day 4-6 she completes review pages again, on her own Day 7 she takes the test
Angel (10th - Algebra 1) - Day 1 she watches the DVD on her own and completes practice page, we correct together, if she has 1 wrong or less, she moves onto review pages, if more than 1 wrong, she completes more practice pages Day 5 she takes the test
So as you can see from our random schedule, MUS has given our family the flexibility to meet each child where they're at. Because MUS teaches math differently and our older daughter struggles with math. We did put her back a year when starting the program. We were previously using A Beka math and she completed pre-algebra in 8th grade, but when we switched to MUS in 9th grade I had her redo pre-algebra with no regrets. It helped her understand the MUS style of teaching and seems to be working for her. We've finally found a program she likes, well......as much as she can like math ;-)
MUS has a different system since it's mastery, the program is really not graded as in 1st, 2nd, 3rd, 4th, etc. They use the Greek alphabet for the different levels and the focus of each level is as follows...
Primer - Having fun introducing math
Alpha - Single digit addition and subtraction
Beta - Multiple digit addition and subtraction
Gamma - Single & multiple digit multiplication
Delta - Single & multiple digit division
Epsilon - Fractions
Zeta - Decimals & percents
Pre-Algebra - Prerequisite: Student should have mastered basic operations, fractions, decimals, and percents
Algebra 1 - Prerequisite: Student should have completed pre-algebra
Geometry - Prerequisite: Student should have completed algebra 1
Algebra 2 - Prerequisite: Student should have completed algebra 1
PreCalculus - Prerequisite: Student should have completed algebra 1, geometry, and algebra 2
Stewardship - A christian approach to personal finance
Honors Books - extra credit, enrichment, or challenge for Algebra 1, Geometry, Algebra 2 (we use these are review with our older daughter)
I'm not sure where your daughter's at with basic operations of add, subtract, multiply, and divide, but I'm thinking if it were my child and they were average, I'd place them in Alpha. This may be review, however, since you're starting a new program, you want to make sure the child has an understanding of how it works and the basic fundamentals. You could always skip the extra practice pages and finish the book sooner. It's much easier to back up in the early grades than to wait until there's problems in high school. I have learned this from experience. There are placement/assessment tests here for MUS...http://www.mathusee.com/about-us/assessment/
I would also check out/play around on the MUS website at http://www.mathusee.com/ They have newsletters, a blog, worksheet generators, etc. Last year, when Angel was struggling with a new concept, I called and she was able to speak with a MUS expert who walked her through it over the phone and helped her understand. I've found them to be a very good and reputable company.
We've tried many math programs including A Beka, Teaching Textbooks, Saxon, Math Lessons for a Living Education, etc. My kids enjoy MUS best of all, I feel they are getting a good foundation in math, and for us it's worth the cost. Bookworm brings up a good point, in that if you have younger children, you will only need to replace the workbook. MUS is a very popular program and you can often times borrow or find it used, though it does retain its value. We've been fortunate to borrow the older high school levels and each year we're purchasing one of the younger levels for our 8 year old that can be passed down to the younger children.
I hope this isn't too lengthy. Please let me know if you have further questions.