My wife was an elementary school teacher prior to having our children. She said that she considered starting a new career instead of going back into education; she thought of nursing as a profession, preferring to deal with blood over dealing with the parents.
She sent me this opinion piece about "what teachers really want to tell parents" today and indicated that it was spot on. After reading it over, I can say that I have seen a lot of these behaviors and issues in my interactions around the school.
One big omission from this list is to separate your identity from your child's performance. I think this is what underlies so many of the other negative behaviors enumerated in that article. From my vantage point, half the time these parental flareups look like "I'm not the type of person who would have a child that turns in a half-assed science project" or "My child must be gifted because I am gifted." Kids fail or are of normal intelligence—even your unique snowflake—and you're just driving your kid's teacher crazy.
I'm not a perfect father, but I feel the best about my parenting when I'm letting them sort things out for themselves. It is very hard to not intervene when they're struggling, but that struggle is necessary for them to truly own their knowledge or wisdom.