Are School Teachers too Specialist

I has worried me for some years (my last family of 3 daughters are just a few years out of school) that teachers seem to be specialised in their subject rather than being specialists in teaching.
Teachers at all levels must be teachers first and foremost, subject specialists second. Whilst at higher levels at university super-specialist knowledges and skills are needed and therefore some inadequacy in teaching skills may have to be accepted, this cannot apply at lower subject levels.
Time and again I see evidence that children at secondary level are not understanding simple basic elements of mathematics and english. These are not difficult skills to teach, so why have our teachers so frequently failed to teach them?
As an educator and trainer in business subjects for many years, I believe the answer is simple.
The basic assumption that seems to be applied by our childrens' teachers is that if a child doesn't learn, it's the child's fault (or maybe the parents').
Sorry teachers... The learning outcome is the teacher's task. Failure to learn means failure to teach! Measure your performance as a teacher by only one criteria. The performance of the child under your teaching.
No excuses are appropriate. I can see no reason why every child of normal (not identified as deficient) intelligence cannot pass all basic secondary school exams. The differences between levels of intellect should only create differences in performance above the pass level.
Time spent answering 'Questions' on Yahoo anly serves to underline this problem. Many kids who can formulate really effective pleas for help are unable to answer easily taught english and maths questions.