I was in the profession for 10 years teaching science and mathematics in middle school and high school, and I've taught mathematics for elementary school educators at the college level. Except for the occasional person with a real calling, the student teachers were able to perform arithmetic only with a calculator and their use of the English language in writing was usually at a fourth or fifth grade level.
Our public school system is rotten from top to bottom. You either have dedicated professionals with deep content knowledge and teaching skill struggling in a system that grows worse each year, or you have people who joined a profession because they have a vague sense that they like children.
With my own sons, I've struggled to find teachers that actually have depth and rigor to their teaching, especially when it comes to math and language. All to often the teachers barely cover half of the scope and sequence in a course, often because they are afraid to demand students work as hard as they must in order to master the skills and knowledge, but also because they didn't understand the concepts the subject requires.
Here is a WSJ article backing up some of what I observed.
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