That depends upon your school district or school system.
Our local school district provides the option to attend school online. This option is essentially the same as attending school, only at home. Same curriculum; same graduation requirements; and a teacher to monitor performance, assignments, and answer questions. It is accredited, so you earn a high school diploma upon graduation.
Interestingly, our state offers a very similar option. I believe the only difference is the source of the assigned teachers.
You could also switch to an alternate online high school (e.g. Stanford; Connections Academy). I believe enrollment in these programs would be considered (for compulsory education purposes) as a private school. Admissions criteria, and tuition costs, are determined by the school.
Yet another alternative is to set up your own curriculum. If online learning is your desire, there are many options (such as Khan Academy, Coursera, K12.com). If you select this option, you will need to pay careful attention to the end product – do you need/want a diploma, go on to college, etc. If college is your goal, you should check the admissions criteria, and ensure your plan meets or exceeds those requirements. The costs and expectations associated with this alternative are much more variable. Once again, careful research is needed.
To implement this alternative, you will most likely need to apply to be a homeschool student. The specific method to do this will be established by your local school district. In the US, this typically involves writing a letter to your school board (from parents or guardian). (Congratulations – that’s often all that’s needed to become a homeschool student!). Usually, you are also required to annually demonstrate your academic progress. (Again, check with your school board for details). Of course, as a homeschooler, you don’t have to limit yourself to online high school.
Enjoy your online schooling adventure!