I created this assignment right before class one day because I was in the process of selling my Chevy Suburban on Craigslist, and I was frustrated by all the spam, scams, and half-hearted responses from potential buyers. I would get two emails a day asking if the item was still available.
Knowing how to answer and create a classified ad is a basic skill every student graduating your high school should have, yet (like most of these kinds of skills) who else is going to teach it besides an English Language Arts teacher? Actually, it would be good practice in a World Languages course, since CL is global.
I have also avoided buying items on Craigslist because of poorly-written ads, so this provides templates for answering an ad as well as posting one.