I know on my PID QL1 there was only 2 of the 16 that had previous diving experience. The majority of the STD courses that I helped teach or that were taught while I was there did not have a significant number of divers on them.
Bare in mind tho, that if you go in without experience, then there is a possibility that you are too uncomfortable to breath underwater and therefore may get removed off course. At which point you will remuster, possibly be allowed to retry the course or you may be given the option to release.
DM