Based on your answers, semesters courses are the best option for you.
Semester-long courses allow you to easily transition to the online environment. It's just like school, but at home. Classes are not quite as fast paced, so you'll be able to take your time as you study. You'll also enjoy fall, winter, spring and summer breaks like your old school. But with a more flexible schedule.
As an 11th or 12th grader, you have been through a lot already in high school. You may have fallen behind, and that's OK! The four courses every 12 weeks will help you stay focused and move through courses quickly so you can achieve your goals. Keep in mind these courses require approval from a counselor.