In Spanish class, while learning commands.
Teacher: Lavate pelo. [Wash your hair].
Student: You lava te pelo. Oh wait, you don't have any.

Teacher, about an orange: Make some lemonade.
Student: I can't. I'm not Jesus.

In Math Class [about a parallelogram]
Teacher: It's almost like you took a square and kicked it.

In Physics:
Teacher: What can you lift in this world?
Students suggest examples:
-wood
-boxes
-a pencil
-weights
-your soul
Class: What?
Teacher: How much does it weigh?
Student: Zero grams.

In History:
The bonus question on a quiz was name a monster from a monster movie. Someone said the Hulk.
Teacher: The Hulk isn't a monster, the Hulk's a good-guy.
Student: Depends which side you're on.