Important answer!!!!!!!!! If this is not spam and you are seriously seeking information you'll need to be clear about what you want. What are you hoping to achieve? Earn a degree? Earn credits in a specific discipline? Get "quick & cheap" credits?
I'm not sure whether online high schools normally allow students to take courses without signing up for their programs. Also I'm not familiar with the US high school system so I don't know how the credit system works there. Are you in the USA? Or another country? I quickly checked James Madison High School (part of Ashworth College, so DETC accredited) and they do allow students to take up to five single courses: Individual Online Courses You'd need to make sure (by checking with your local school or board of education or whatever) that any courses you took online would be accepted to fulfill the requirements that you need.
You never know, we attract higher than the average level of trolls.:AR15firing: The first thing I'd do is figure out which specific courses you need and then figure out if they'd let you take them at your local community college.