Personal guess has the following reasons:
1, parents worry too much.
Many parents are very concerned about their children's academic performance. As long as children's academic performance declines, there will be anxiety. I will analyze the reasons for the decline in my grades with my children. Normal parents will treat this matter rationally. Some irrational parents feel that their children have studied very hard these days, but their grades have not improved. It may be that the teacher didn't teach well, or it may be that the teacher was eccentric in early summer. After all, there are many children in each class. Once this idea appears in parents' minds, it will take root in their hearts for a long time, leading to a bad relationship between parents and teachers. Especially the children whose grades are similar to their own have improved, and parents' dissatisfaction with teachers is even worse.
2. Some teachers' inaction
In life, we often hear that some teachers in some schools are not doing anything and the education work is not in place. Teachers in some public schools, in particular, have a system, and poor teaching will not affect their salary. They just go to work on time and attend classes on time. He doesn't care about the specific content of the class, and students don't care whether they learn or not. There are even some teachers whose focus is not on educating students, but on striving for progress and rights.
People have followed suit.
Some parents' evaluation of teachers is not objective and easily influenced by other parents. In the communication with teachers, I don't pay attention to teachers' educational achievements and work, but I am willing to listen to other parents' comments on teachers. If some parents think that this teacher is not good, it will affect others and make them have a poor evaluation of the teacher, which will lead them to stand on the opposite side of the teacher psychologically.