As our kids get older, it is important for them to become familiar with different methods of learning and having different instructors. Online classes is a great way to accomplish this. The format of these classes can vary from live classes have student interaction to recorded classes that can be done at your convenience.
This is also a great option for those subjects that you want to pass off to someone else. I know that writing, for example, can be so personal. We have found it best to have someone else teach and grade writing. Also, math and science are things that some people are strong in, others are not. Some parents sometimes feel like giving up on homeschool once kids reach a certain level of academics - you don't have to do that. There are resources out there at various price points.
Maybe your child isn't ready for a classroom environment, or you don't have time or there isn't anything close to you that fits your needs. The Internet has so much to choose from regarding online classes - you could spend hours finding classes, researching classes and reading reviews of classes.
I have listed some great options below.
We have participated in several of these over the years. It is important to find the right fit - there are some that I would never do again - they did not make the list.