It is no surprise that everyone in the class is not on the same skill level. The solution, assuming that there are enough people, is to have beginner classes. When everyone is on the same page, the instructor can focus specifically on basics that most students that are more experienced take for granted.
Even in a beginner class, not everyone progresses at the same pace. But at least the slightly more advanced beginners can help the newer students.
In an environment with a smaller student body, this may not be possible. It should be accepted by the more advanced students that the basics are going to be mixed with the advanced moves.
Now a series of half guard sweeps, everyone should know: