I've usually told my kids, when they got into trouble, "you've made this bed now you'll have to lay in it".
There were two times I didn't. About 15 years ago, (give or take 5) my oldest, then about a 3rd grader, brought home his final report card for the year. It had an INCOMPLETE behind ART. I asked the typical thing that most fathers would ask. "You're taking art"? I asked him what the problem was. He was so mad, his eye's were red. "She said I didn't hand in my last project". "I did". "She's lost it". I have always hesitated to go to school and complain. Mostly because most of the administration have always been good friends. What to do? The teacher was widely known for being disorganized. I called her and told her who I was. I said "He says he turned it in, could you conduct another search for it". I got a call back in about 30 minutes and it had been found stuck to the back of another project. She'd be happy to change the grade.
The other incident that comes to mind was when my youngest was in High School and he turned in a book report at the end of the year. It was important to him because he needed a certain average to avoid taking the semester test, and he was teetering on the edge. He got his report back and the grade was not good enough. I had proof read the report and felt that it was not bad. When I started to study the paper it dawned on me that there had been a substantial error in addition on the -2 here, and the -1/2 there and so on. AND the one that got to me was the last question. It was something like, Give your opinion of the book and would you read another book by this author. In so many words my son had related that, no, he didn't like the book and wouldn't read another by that author. His Opinion was apparently wrong, because he got the full 4 points off.
I was going into a boil, I could hardly breath I was so mad. The teacher had obviously little regard for either this assignment, grading, or my son. It didn't matter, I was going to call the principal in the morning and get a meeting with him, and the teacher, and my son, and I. I slept on it. In the morning my mind was clear. Forget the meeting I thought. I said to my son. "Take this paper back in and say these exact words, My Dad thinks you may want to re-add the number of incorrect. And he was also wondering about the last question". He brought the paper home that night, it had been recorrected, and I think he had about 16 points added to his grade. Oh yeah, his opinion was no longer incorrect.
It taught me a lot about confrontation. When I'm ready to fly off the handle, in a public way, I sleep on it, and can usually come up with a plan to get my way without having to say something to regret the rest of my life.
Oh yes, the teacher was a good one, I think, but was just going through the motions until she figured out that someone was watching.