Khan Academy Highschool

Create and account at Khan Academy. Then come back and click on the highschool subject of interest to access the correct path for the course. Observe the different concepts covered. Then click on the first category and start your journey there. I don't recommend to click on the link that says " Get a personal path through ......"  as it might prove to be very challenging and discouraging for the student. Do it when he/she has done half of the course :
Pre-calculus
SAT Prep

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an example of how to study with Khan Academy
Khan Academy offers free online lessons in the form of videos and practice concepts marked with a star. My kids are getting to really learn highschool math with Khan Academy and by doing the exercises and completing them  highschool math is sinking in the right way to prepare them for college. I have my kids do the exercises until they pass each exercise challenge marked with a star. The star looks like an empty star, after they complete the exercise challenge the star gets filled in with blue. Give them credit for all the filled stars that go along with the different categories.

Highschool math wasn't my strength when I was in school but homeschooling my kids has really helped me get better at highschool math. There will be times when they need your help so prepare yourself to help them. You can follow along with these courses too! My kids are doing good using Khan Academy, their effort, and their mom's help.