As you mentioned the method of teaching is very important but explaining the most successful results depend on many factors:
Every teacher develops a particular way of going about the complex task of teaching.
The way one introduces a topic raises a question, makes assignments- all these and hundreds of other behaviours together make up a teacher’s classification by researchers, colleagues, and students. Traditional teaching style is described as a teacher-directed approach while in transitional style, both teacher and students are expected to assist each other during the teaching and learning process.
The logical and proper relationship and friendship of teachers' ratio with their students' achievement and retention of learning should be considered too.