have had both kinds of instructors mentioned, ie: can't deal with behinders or aheaders. also, have had many instructors who recognized the different levels and were able to help everyone. different people with different skills. regardless of the instructor i just try to keep a positive attitude, get as much as i can from them, then go home with a new project.
just took a class from anelie belden on her thoroughly modern dresden. great instructor, great project. she gave group instruction, worked closely with each of us at our own level. for those who got each task done early she would come by and give additional instructions. for those who were struggling she would come to them and give additional help. love my new dresden plate table topper and plan to do more.
hope you find an instructor you enjoy. keep trying as there is lots to learn out there.