My daughter has attended BC class for 2 months, I can feel the patience of instructors. In Montessori classroom, you may not expect the instructor (they are not taking teacher's role as in traditional classroom) to interrupt the child too much but kid learn through observation & replication from others by himself. Instructor or parent's is just an assistance or demonstrator to kid on work tasks. Thus, as long as the environment is planned in classroom with patient instructor, I think this is not necessary to follow particular instructor all the way through.
My daughter has hanged around classroom for almost 2 months and just started to engage in the happening in class. however, through the instructor's feedbacks from time to time, I know instructors keep observing her behaviour & know the progress of change