When I was studying educational research, it seemed that most sources agreed that - apart from individualized tutoring - decreasing class size was one key to better learning. IIRC, the magic 'threshold) was 12. (Mob vs. seminar?)
Of course, teacher's real engagement with their subject and students, and teaching experiences (if they're in tune with what works, and also trying new methods) are important. As is whether their districts encourage (and can afford) innovation (in learning materials and media for example).
Regardless, teachers have to begin at the level of their average student (TBD); if the spread is too wide, some will be bored, some challenged. All of this is a lot to ask, moreso for teachers with outside lives to live and grow themselves also.
Of course, teacher's real engagement with their subject and students, and teaching experiences (if they're in tune with what works, and also trying new methods) are important. As is whether their districts encourage (and can afford) innovation (in learning materials and media for example).
Regardless, teachers have to begin at the level of their average student (TBD); if the spread is too wide, some will be bored, some challenged. All of this is a lot to ask, moreso for teachers with outside lives to live and grow themselves also.