Getting started with high school science learning
For science, first address the requirements for your goal - does your community college or training program have requirements? Do they need to pass a test on certain subjects for admittance? Also, if your teen has been in public school, what science did they cover already? Did they like it / learn it well?
Second, what is your student interested in? These interests will make learning easy, fun, and hopefully useful in a future career. Ecology? Smelting? Rockets? Psychology? Veterinary science? Astronomy? Marine biology? The list is endless.
Third, what are your general goals for being a well-rounded, educated adult? Enough biology to discuss issues with a doctor? Enough chemistry to understand a nutrition article? Enough physics to build a garden shed? The list is different for every family.
When you have a few things on your "probably" list: Pick one and get started. You can do DIY studies, or find some curriculum or classes to use.
DIY Science units: Find a few books at the library, or a chapter in a textbook, documentaries or YouTube videos. Dive in and see where it leads! This may mean you as a parent need to pre-screen some resources, or if your teen is up to it, they can do that too.
Planned science classes or curriculum: These will be available in the more common high school science topics, such as Biology, Chemistry, Physics, and Earth Science. For print-based studies, try a used textbook from Amazon as a starting place, such as Holt Modern Chemistry (used $15), Glencoe Physics (used $10), or Miller and Levine Biology (used $10). Real Science Odyssey also has a great made-for-homeschool Biology book.
For online science, Try Biozone for Biology or Anatomy, they have print, digital, or hybrid. Outschool offers many high school level full semester classes, just search for age and topic on their website. CK-12 has free online lessons (reading and questions) in Chemistry, Biology, Physics and others. NextLevelHomeschool has online classes in Marine Biology, Chemistry, and Anatomy.