> Second because of the hubris: what makes you think that you are actually more qualified to
> teach your children than a professional?
Having gone through the US education system (assuming the schools I attended, and the schools of the people I have spoken to, are at all representative), that's likely a safe bet. Most of the teachers I had over the years barely understood the material enough to present it to the students. Many, many teachers struggled to even answer basic questions. When I was younger, I had just assumed I didn't know enough to understand their answers. Later on, when there was material I already understood fairly well, it became quite obvious they had no clue what they were talking about when they gave completely nonsensical answers.
This is due to the design of the system. The system isn't designed to identify the best teachers are reward them, while removing the bad teachers. It's designed to reward those that manage to go the longest without doing something stupid enough to get fired. I have no idea how the teachers that are actually competent (they do exist) are able to stand it... maybe they can't and that's why.
There are many other problems beyond just the teachers, though.