I have looked over "Discovering Mathematics 1A/1B" thoroughly, and I think it is an excellent math program that follows the format of Singapore's Primary Math well. I spoke with Carrie about several different math paths. I will try to explain them here...
When dc have completed Singapore's Primary Math 6A/6B (or its equivalent in another math program), this would be a path they could take, getting as far as they get...
Discovering Mathematics 1A/1B: Pre-Algebra
Discovering Mathematics 2A/2B: Algebra 1
Discovering Mathematics 3A/3B: Geometry
Discovering Mathematics 4A/4B: Algebra 2
Advanced Math: Pre-Calc - Trig (first half) and mostly Calc (second half)
Using Video Text is another suggested option. Students always need to start with "A" in Video Text, as it is foundational. This would be the path dc could take with this option...
Discovering Mathematics 1A/1B (or may possibly skip this if they are a very strong math student)
Video Text A (pre-Algebra), and BC (Algebra 1)
Video Text DEF (Algebra 2)
Video Text ABC (Geometry)
Video Text DEFG (Trig/PreCalc)
Let's say that a student begins with "Discovering Math 1A/1B, and then wants to make a change to using Video Text. An appropriate place to make the change would be after using "Discovering Math 1A/1B, as then students would not be losing any time having to begin with Video Text A.
Another appropriate place to make the change from "Discovering Mathematics" would be after "Discovering Mathematics 3A/3B". Students could do Advanced Trig with a different math program.
Here is a link to a post where Carrie mentioned some information in regard to upper level math as well...
viewtopic.php?f=6&t=5500
I hope that this may help you out in some way!
In Christ,
Julie