When children have reached the point of reading and writing well, working on vocabulary development can change from previous years. I have a variety of ideas for high school vocabulary development that can help you with your teenagers. You can read through them, and see if you can find suggestions that will help you with your child, in your unique

Homeschooling high school is a challenge. College prep is an additional challenge on top of that. Many parents struggle because they don't know HOW to create a high school plan that will help them get their children to their intended destination (graduation, college/career, independence). 

Most people create a high school plan on the fly, picking up bits and pieces of

Finding challenging material for profoundly  gifted children can be difficult, particularly when students are working at a college level. Consider carefully whether MOOCs  might be a good fit.  You can find more information about MOOCs in my post, Massive Open Online Courses [MOOCs] For Homeschool Students.

EdX works well with younger students who are profoundly gifted and need a challenge.