Here you can check out the National Exam overall marks by teaching institute. While it does not tell you the entire story, it can be a starting place. Take for example if you have ESL students in your class. We had a couple of things happen in our class - ESL being one of them, that people did not write at the last minute or had to re write the exam, bringing our school mark down when it really wasn't.
http://www.clpnbc.org/index.php?dbq=10#1131061
Yours in nursing,