Saylor's College Algebra not ACE recommended?

[Merlin]

My advice for a teen is to use the curriculum of choice (I'd use Khan Academy-free) and then zip through the Modern States to get the free CLEP voucher.  Worst case, the voucher program expires, you're still better off with CLEP credit over NCCRS or even ACE unless you're already picking a target college - at that point choose whatever is accepted.  If you're still playing odds, CLEP beats ACE/NCCRS.
Edit to add:  depending on the regular math curriculum, once you're past Algebra 2, the "next" book usually gives a bit of pre-calc.  You don't need a ton of precalc for that exam, but solid on Algebra 2 for sure.

That actually makes good sense... assuming they have local CLEP testing opportunities. I prefer CLEP testing myself, but unfortunately, some of us live in areas where the only nearby test centers are closed to the public, or there are no testing centers at all. I always forget to suggest CLEP due to this.