The reaction of students when a teacher farts can vary greatly. Younger students are more likely to burst into laughter without much thought. They might find it extremely hilarious and have a hard time containing themselves. Older students, on the other hand, might be more reserved. They might exchange knowing glances with their classmates but not laugh out loud. Some students might also feel embarrassed for the teacher and try to act normal so as not to make the teacher feel worse.
Well, there could be different reactions. Some might be shocked at first and then try to hold in their laughter. Others might be more mature about it and just pretend not to notice. If the teacher is well - liked, students might even feel sorry for the teacher's embarrassment and try to make the situation less awkward by focusing more on the lesson. There could also be a few naughty ones who might make some not - so - nice comments under their breath, but that's not very common.