Mastery of the subject matter is key. Students must be confident in their abilities. They also must have sufficient breath in the subject to be mathematically literate. It seemed that at all levels that instructors were concerned about the questionable algebra skills in their students. There was concern about the mathematical level needed for certification of K-8 teachers, many of who teach beginning algebra but may not taken much mathematics themselves.
Instructors have their own set of problems.
Variation of instruction occurs at all levels and can be due to many factors. Instructor's interest and focus within the course may influence student outcomes. Too much of a gradation of ability within a class can make class management very difficult. There is often pressure from students, parents, others to keep the amount of homework down. It was also noted that there is quite a bit of competition for getting students into advanced classes both at the high school and college level.