Five to ten most times. As little as three on slow nights (Silat not being that big here) or a couple of dozen when the whole school gets all its clubs together.
When it's a holiday, there could be as few a 4 or 5 people (including the instructor) - on a 'busy day' there could be over 20 people. So I'd guess it would be about 12 people on average.
Counting my teaching partner and Myself, we have about 15 regular participants in classes and another 6-8 folks who wander in an out sporadically. So, all total about 21-22 students but on a day to day basis the regular class is 4-6 students at a time.
We have a traditional little "backyard" silat school where we prefer to screen students and insure quality over quantity. I suppose I also like to keep the group small and tight knit. I prefer that we operate as a small group of friends who are invested in the upward growth of all involved. I have information out there that lets someone searching for pencak silat know we are around but folks have to go through some screening and jump over a modest hurdle or two in order to be invited to train. Those who have jumped these hurdles almost always seem to show up once invited and generally turn out to be pretty good students. Those who wouldn't probably would never have quite "fit" with our group's collective "personality".
We are a pretty small group and have no aspirations toward achieving the membership numbers enjoyed by some of the more commercial or mainstream martial arts schools around the area. Which suits us fine.