My daughter goes here and we absolutely love it. In-fact, everyone we have talked to who goes here raves about what an amazing school this is. My daughter and I did a lot of moving and she has been to many schools already in her life. Horizon is by far the most comprehensive school she has attended. If you are advanced in a certain area, you will be in a class with older kids who are at your level. If you need help with a subject, you won't be left behind, you will get mandatory extra help with that subject.
I can't say enough about Horizon, but be forewarned there is a waiting list and I know people who have had their kids on the list for years. It's worth the wait once you get a child in though.