If you want to teach the concept of sorting, then I believe you must teach at least two different ways of sorting -- otherwise the students will think that sorting is just about the one way you taught them.
I think the students would get the most value out of learning a classic O(n^2) algorithm (preferably insertion or selection sort, but please not bubble sort, which has no justification for being used in real applications), as well as a divide-and-conquer, O(nlogn) algorithm such as quicksort or merge sort.
If you're worried that these sorts will be too hard to teach your students, have a look at these activities from Computer Science Unplugged, which are designed for elementary school students.
