答案

Times have changed. In the past, what the teachers said must be right. But in the modern society, students are brave enough to doubt the teacher or even conduct a fierce discussion in class. And I believe there are some advantages of in-class correction. 
To begin with, I have to pick out the mistake the teacher having made in class in case other students are misled. This happens frequently. During the class, the teacher may from time to time make some mistakes, some of which are oral. Good students who are in good command of knowledge will notice the mistake and correct it by themselves. But the other students, especially those who depend solely on the in-class notes, may suffer. They are wholly concentrating on the class content without noticing the mistake and may rely on the wrong answer for test preparations. 
Moreover, in case other students have similar doubt as I do, class discussion may help us understand the content better. There are certain situations when what the teacher is uttering confuses most of the students. If I can raise question in class, the teacher can conduct an in-class discussion and this is beneficial. On one hand, we will find out whether what the teacher said is a mistake or a misunderstanding. On the other hand, in-class discussion may reinforce our memory concerning the discussed topic and help us better understand the confusing point.
Furthermore, characteristics of teachers vary and I prefer to make an in-class correction in case the teacher welcomes in-class discussion. Learning is a process requiring interaction between the teacher and the students. In terms of the students, when they are active enough to raise questions and notice the mistake the teacher has made, it is a strong indication that the student is fully involved in the process of learning. Therefore, most teachers welcome in-class correction and will not be annoyed by the interruption. And concerning the teacher, there might be some misunderstanding of class content in the knowledge base and students’ correction may be humiliating, but helpful. 
To end up, although in some cultures which claim the respect to teachers, in-class correction may be regarded rude and disrespectful, most teachers welcome in-class discussion, for the sake of both teachers and students.