My DS is a junior in high school and my DD is in 5th grade. In all of that time, there has been only 1 really, really bad teacher. She was awful. She was mean and a yeller. Everyone knew it too. Heck, she would yell at parents. My normally school-loving student absolutely hated school that year. My DH and I sat him down and told him that as his parents who loved him, our first instincts were, of course, to remove him from the class. BUT, we weren't going to. We told him that in every aspect of life, he was going to meet/work/deal with people who he didn't like or get along with. He was fortunate that he only had to deal with this teacher for 1 school year. We told him that he could come home everyday and rant and rave to us and we would listen. We validated to him that we knew she was awful but it didn't mean we would run from it. After that, every teacher would seem like cake. You know what, as a junior, he now compares every teacher with that 5th grade teacher and they all seem like cake by comparison. I do know there are times that a chance might be required, but I think we are often too quick to make that change for our children.
Regarding grades, I am a "suck it up buttercup" type of parent. I would have been more concerned about why my child had made a 44 on a project. Honestly, my kids always seems to generally know what other kids make on tests/projects in school. Heck, just to freak out some of the parents on here, my DD's 5th grade class exchange papers to grade. Having papers on her desk with the grade showing wouldn't have even made my radar.