Can my child enroll in a single course or participate in band or sports at our local public high school?
This is a decision solely up to the public school. Most will not allow homeschoolers to participate unless they belong to a public independent study program. If you are not willing to join a public high school ISP, or one is not available in your area, you might check with private schools and programs in your area, or look into participation at the community college level. For sports, the California Interscholastsic Federation (CIF) makes the rules for CIF affiliated schools, which includes all public schools. They have stated that homeschoolers are eligible to play only if they are enrolled in a public independent study program. If you intend to participate in sports at the college level, read the frequently asked questions section of the NCAA web page, and remember that there is a limit on the number of semesters a college student can compete, and community college sports do count towards that limit.