While some teachers are just plain incompetent or ignorant, that is not the only factor leading to poor performance. Here are several more: (a) teacher training is poor. Far too much time is devoted to topics like philosophy of education and social issues, too little to things like subject knowledge, normal and abnormal language acquisition, how to teach reading, and so forth. For example, I know of teacher education programs in which teachers, including those destine to be elementary school teachers, are not taught how to teach children to read, which is probably the single most important thing they do. In one case, as part of a seminar, the students read and discussed two papers on approaches to the teaching of reading; that was the entire extent of their training in how to teach reading! (b) excessive diversity of students is very difficult for a teacher to deal with. You only have the time and resources to individualize instruction so much. If the students are at very different levels, even a good teacher can't do a good job. The mainstreaming of students with disabilities has exacerbated this problem. I don't mean to suggest a return to rigid tracking or to dumping all special needs kids in separate classes or schools, but we need some combination of classes that are more homogeneous as to level and ability together with adequate support (in the form of teachers' aides and other resources) for special needs students. (c) school administrations and government departments of education often impose poor curricula and materials. Greater competence and less political interference in the education bureaucracy would be a boon.