As former teacher, I assume my students know nothing. You will find "aces and spaces" in any group. Try to find one block that has some of the problems in it and teach that one first. You will soon find out just how advanced they are. Also, as has been said, talk to the shop owner and try to talk to the students you will be teaching to see if they have experience at all. I had one lady in a beginning quilt class who did not know how to thread a needle. She ran yards and yards of thread off the spool and attempted to thread the needle.