Escape behavior happens when someone wants to get away from something they don't like. When a student wants to escape, they're trying to avoid doing something they don't enjoy.
If in the past, the student did this behavior and it made the bad thing go away, they're more likely to do it again in the future to avoid the same thing. The removal of the task functions as a negative reinforcer and increases the likelihood that the student will engage in this behavior to escape/avoid future work.
For instance, when Ms. Smith gives Johnny a math worksheet, he tears it up and throws it away. As a result, Ms. Smith does not make him do his math homework.
In the future, Johnny continues to engage in this behavior, and everytime he gets a math worksheet, he tears it up again to avoid doing it.