Private candidates take exams through British Council, not only them if you contact a school to take exams through, if that is an unregistered one, they will just act as an agent, doing the things for you otherwise, the same procedure follows, i.e. the exams are basically between British Council and you, no name of the school will be mentioned. Candidates from unregistered schools are just like private ones. But in the other case, if you contact a registered school, I don't think they would let you do so without becoming their student. I am a private candidate as well, and I've taken exams many times by contacting British Council. You must keep in touch with the site to know when the registration form will be available, sometimes the range of days to register is just very short, so much that after the results of June 2015 is announced, you must check the site every day to look for the form although usually it is available next day to the result day of previous session. After you get the form, fill it out, you would know the fee structures all written there, then send it to British Council through any branch of Standard Chartered Bank.