One of my readers asked me about Horizons math, so in answer to her question, I am going to just going to share my homeschool math history.
My 16 year old used Horizons math from grades 1-6, then she started Teaching Textbooks (TT). Horizons used to stop at 6th grade. She has used TT for grades 7-10, and I plan for her use TT one more year. She has Algebra 2 left. For her (and my other children's) senior year, I plan to have them take Intermediate Algebra 1st semester and College Algebra 2nd semester at a local community college and earn dual credit (high school math and college credit as well).
My 13 year old used Horizons math from grades 1-5, and then I switched her to TT in grade 6 (I originally considered 6th grade Horizons to be very difficult). She is on track to continue with TT through 11th grade just like child #1.
My 12 year old used Horizons math from grades K-4, and I switched him to TT in grade 5 (I had a kindergartner and freshman in high school that year, and I chose TT because he could do it completely alone.). He is now in the 6th grade, and after doing 5th grade in TT and half of 6th grade in TT, I decided that the TT in the lower grades was just too easy, and I put him back in 6th grade Horizons. Horizons 6th grade lessons are 3 pages per day. He began in January doing 2 pages per day, and I plan for him to take about half or more of 7th grade to complete this course. Horizons now has a 7th grade course, called Pre-algebra. I will put him in that course in the latter part of 7th grade and have him complete it in 8th grade. For 9-11th grades he will do TT Algebra 1, Geometry, and then Algebra 2, and then the college classes.
My 7 year old has completed Horizons K and is currently doing the 1st grade book. My plan for her and for child number 5, who will begin K next fall, is to do Horizons for grades K-8, taking three school years to complete Horizons 6 and Pre-Algebra.
My opinion overall of TT from Pre-Algebra on down: TOO EASY! When my older children switched from Horizons, they did not learn one new thing for an entire school year! Not one thing! I could have easily skipped a grade when moving them over, but decided to just let them have a "review year".
I have been concerned about the difficulty of TT in high school, but did not know of another program to use. I train my children to be independent learners, and I need a course that can explain the concepts to the student. TT does this, but I was unsure of its thoroughness. In my local homeschool circle, I have two friends who are math majors and teach at community colleges part time (they also homeschool). One of them uses Math U See in the lower grades, the other uses Horizons. For high school level courses they are making up their own math curriculum. That is not an option for me!
A couple of months ago, one of my math friends, Kathy, came over to my house and actually looked at my Algebra 1 and Geometry TT books. She studied them for quite some time and came to the conclusion that they are the best of the choices that are out there for non-math teaching parents. She recommended that I do just like I said, use Horizons (which she felt is best) until 9th grade, and then use TT for 9-11, and then the college plan I talked about. In order to adequately prepare for the ACT, she suggested that I purchase an ACT math review book from somewhere like Barnes and Noble, and have my 10th graders and up work in it for 10-15 minutes a day. That will help them be familiar with how the questions will be asked on the test. She felt like they would do fine in college, since they are self taught....if they can master a high school math course independently, then they will do fine on the college level when they have a teacher to explain things.
If my children were/are interested in a math career, I would use the TT Calculus book instead of taking the college classes their senior year, or begin Algebra 1 in 8th grade and then do Calculus in 11th grade, and college classes in 12th grade.
So there you have it! My opinion on Horizons math and Teaching Textbooks. As in all academic subjects, my goal is for my children to be independent learners. If I can teach them how to learn, then they can succeed in any area. I have written about this before--teaching my children to become independent learners begins in Kindergarten. It is a gradual process, and by the 7th or 8th grade, they can complete almost all of their schoolwork independently. I am not trying to be lazy or anything, I am just trying to equip them for a lifetime of problem solving and self-educating.
Have a good math day!