It gets really hard when you have a mixed bag of students. Pushing each group gets tough. There are times when one group or the other will get the short straw. Sometimes that means the group not really wanting the full extent of learning will get pushed beyond their comfort zone. Sometimes that is a profoundly good thing for the person and they find another gear. Sometimes, if done too often, it may push someone from the other group away. It is just a reality in the process.
It is imperative for an instructor to learn how to realize who is who and work the ones who want more accordingly.
(EDIT: I clicked POST before I added any content.)
Agreed. This is where some schools do well to add "advanced" classes, and other segmentation. A class that allows for folks who want to train hard and fast, a class for deep dives into technique, etc. The trick is knowing which segments to serve.