If I a in a classroom or a meeting, and the teacher or the meeting leader says something incorrect in my opinion, I will wait until the class or meeting is over and the people are gone, and then talk to the teacher or meeting leader. 

There are two reason support me, the frist reason is when I say my opinion after the class or meeting, if my opinion is ture, then the teacher or meeting leader won't be so embarrassing, and also can explain his wrong in the next class or meeting. For example, my friend work in a big company, when the boss was told in the meeting, my friend find the correct in the boss's talk, then my friend interrupted the meeting and says the boss was wrong. Few time latter, everyone know the boss was wrong and laugh, the boss was so embarrassing and angry, then my friend was leave away this company. If he wait until the meeting is over and the people are gone, and then talk to the boss, he won't keave the company and maybe get the more salar. 

Secondly, when I wait until the class or meeting is over and the people are gone, and then talk to the teacher or meeting leader, eventhough it is my mistake, I also can get the knowledge and can get the good impression with the teacher or meeting leader. For example, when I still study in the high school my teacher take a mistake then I told her after the class then she explain her mistake in the next class and always think I was very smary, then if I have something can't understand she alway teach my hold a lot of patience, until I know the answer. If I say nothing, then I won't get the knowledge and teachers trust. 

All in all, when you find the teacher or the meeting leader says something incorrect In your opinion, you have to wait until the class or meeting is over and the people are gone, and then talk to the teacher or meeting leader.