I haven’t homeschooled above 8th grade, but here are resources that friends with high school students have used.
A la carte classes:
You can create your own transcript for high school if you go this route – email me for resources if needed.
Study.com – lots of full courses. This site is organized and is popular with a lot of homeschoolers currently – 59.99 a month per students. Middle school class options as well.
The Lukeion Project – ages 10 and up – classical courses for middle and high school
Build Your Library – full year secular homeschool curriculum for 9th grade.
Edx.org: free high school courses (including AP). These are worth a look.
SAT Prep – Reasonably priced test prep material that I’ve seen recommended in secular homeschool groups.
PrepScholar – highly recommended test prep online. Reviews for this site are really good.
Outschool – choose courses based on ratings and interest. My kids love art classes by Shannon Kline Collins and Jennifer Rowe, for example
AP Homeschoolers – AP Online classes
Blue Tent – full year courses (usually have to sign up in March of prior year)
Full school options:
iUniversity Prep (for Texas residents) – recommended by several friends whose kids went on to excellent universities from this program
Stanford Online High School – this is a $$$$ program but an educator I trust recommends it and knows some of the people involved.
Williamsburg Academy – free in some states with homeschool charters