It might be difficult to do that because even though you could be fluent in the language, the teachers may still question your capabilities and also the fact that you didn't do the preliminary course might hinder your chance. But, if I was you, I'd talk to the principal, language coordinator at your school and Saturday School of Languages (if you're doing it through there) to try and make it happen. The sooner you do this, the greater chance you have of being able to do the course.