To illustrate that just a little better, one can ask what does an effective school take. Well it can take a good curriculum (aka text books)and it can take good teachers and a good school. Now one can have good books and bad teachers (For example a teacher sexually abusing students), one can have good books, good teachers and bad schools... (rats in the schools, hungry students, poor nutrition in schools, fighting among students). One can have good teachers, good environments and bad curriculum. (This might happen in a communist/muslim/Hindu country with propaganda. The students have a supportive family environments, teachers who care, yet the school books are teaching things that just don't work or are false.) So there is a complex balance one needs to have. Getting this balance right is difficult. Even in this illustrative example, really there are probably about 20 plus factors that go into the perfect combination. (personal security of the students, family support, teacher support, access to technology, natural disasters, ect).