A classroom runs at the speed of the slowest class member you are willing to accommodate. If you go all the way to the bottom, the rest of the classroom is deprived of education at the level that any one of them could attain. I prefer running a self-paced arrangement so the fast ones can achieve to their limits and provide peer mentoring to the less intellectually inclined.
In a former life I taught Adults with ages from 24 to 64ish in each class. While conducting these intense 7 day classes I would have half the room saying “Slow down, slow down”, while the other half was saying “Speed up”. It was a constant issue and when I asked other Instructors how they handled this, They virtually all said they would teach to the lowest common denominator. I couldn’t do this. I felt the advanced learners paid good money and were entitled to a higher level of education and that would pull the others up. I found a balance that would push and satisfy the high level folks while circling back to pull the others along. It worked for me.
Not all Teachers, or even that many of them, are actually any good at teaching. I was told numerous times by highly educated successful students, Phd’s, Engineers, Professors etc, that I was a natural teacher.