> One of the few lessons to stick with me from high school English was during the lesson on irony, when a student asked "Is sarcasm the same thing as irony?" and the teacher thought about it for a moment, before responding that, yes, it is, kind of, but it's the lowest form of irony.

Properly speaking, sarcasm often uses verbal irony, but sarcasm does not necessarily involve irony. Though maybe that definition is changing; its not that uncommon to see "sarcasm" used as if it were equivalent to verbal irony.