Contractions vs Contractions

My tenth graders were working on an expository writing essay today, and one girl stated that she always forgets that she's not supposed to use contractions in her writing and that she always uses them...well, another girl chimes in and asks, "Aren't there two types of contractions?". To that I answer, "Well, I guess so...you have the negative ones that use the word 'not' and then the other ones that use words like 'have' and 'will'." She tuned up her nose and said, "No, I mean like the contractions when you're having a baby"...**blank stare from EVERYONE in class and then we all laugh at her**

disclaimer: you may have had to be there and you may have to know the student to find it funny...