I concur with what everyone has said regarding taking the PSAT, SAT & ACT.
My daughter is a math whiz and did a lot better on the SAT than on the ACT. She earned a partial scholarship to a local Baptist college.
I would recommend that after your child has taken Alg. 2 you have her take the CLEP test for Col. Algebra. Take the CLEP tests after each dual enrollment class. Your child could be a sophomore in college when they begin. You can take the CLEP tests at any age. I didn't do this with my older three but will with the younger 3.
I know what you mean about fellow homeschoolers not being concerned about college prep in 9th. In our area it is the same way.
The college board site does have a academic plan starting with 9th grade.
http://www.davidandlaurie.com/main.html
These folks teach clep prep classes.