Correspondence honors courses
I work in the 5th largest school district and we offer a huge summer school program. However, there are no honors courses during the summer. When students want to take an honors class to either make up a lousy semester or take a whole course to get ahead, I refer them to correspondence schools. I would only recommend this to a high achieving, extremely self motivated student that is obviously very strong in math. This is not for everyone! Many have finished successfully. The ones that don't finish will readily admit it's due to laziness rather than lack of ability and understanding.
My son took Alg I honors in 8th, Geometry honors through Stanford distance ed the summer preceding 9th, Algebra II/Trig honors in 9th, Precalc honors in 10th, and then took Calc. I and II at the community college during his 11th grade year. His senior year he took one semester of Calc III and has nothing right now.
University of Miami Online High School (which has just changed its name to Kaplan College Prep School) offers Alg, Geo, Alg II, Pre Calc, all honors, and Calculus AB and BC if anyone should so desire to get ahead. Stanford also offers honors math classes. BYU Independent Study has more affordable courses, but they're not honors. If you're great at Algebra, you can take Algebra II and move straight to Trig or PreCalc the next year.
If you are interested, check with your school district and see if they will accept these classes. You can PM me and I'll send you the links.
From a parent's perspective, I figured what the hey, they aren't doing anything during the summer anyway. I have twin 9th graders, and one is doing exactly what his older brother did (although he has his eye set on CGA) and the other could care less about pushing himself and wants to get a job and make money this summer. I suggested he do a math class this summer to get ahead and his typical resonse was, "What for?" As I said, it's not for everyone...