What kind of driving course is that? What does it include? I always paid per lesson, can't remember exactly now, was a few years ago.... but why shell out that much money up front when you don't know how many lessons you'll really need?
I never heard of any blacklist of driving schools myself, where did you hear that?
I used the school with the yellow cars at Dreispitz - these guys
http://www.lerncenter.info/
They're not the cheapest but they were excellent and have English speaking instructors (and many other languages too.) I passed first time with them (as compared to having previously failed four times in the UK

)