As probably for many other teachers, this is a hot-button topic for me. The first 6 years I taught, I'd never heard of the concept. No students asked for a retest; I didn't know such a situation could exist. My next 6 years of teaching in another state and another type of school, I got indoctrinated. Eventually, I felt I "bowed" to the pressure and allowed retests. I finally worked out a system that sat "okay/well" with me: anyone with all their homework assignments turned in could retest, and your final grade on the test is an average of your 2 tests, so technically, your grade could go down if you did worse on the retest.
One reason I didn't like retests was that I saw too many kids either not studying for them, or not studying for the original test, knowing they could have a do over.
Now that I've moved schools, I gave no retests. You got what you got.
This summer in Philadelphia, I happened across this book, and there was a discussion on retests of some sort. As I felt my hackles rising, I ran across a statement that gave me pause:
If a kid fails a test or does poorly and shows they don't know a particular concept and you just move on, you are in essence saying that you're okay with them not having that knowledge under their belt, that it's okay not to ultimately understand something in your course.
I don't know that I'll move back to retesting as I've done before, but I want to think further on this idea for next year. I know there's been discussion on the blogs on this, and I've been reading it, and I think I need to find something that works for me and is manageable in my classroom and that I buy into; otherwise, obviously, I won't effectively implement it, and it's doomed to fail.
My initial kernel of an idea is to have a list of concepts they need to know, and by each concept I have 2 boxes with a room for the date of success. This may be on box.net or something with each student's name in a chart, and when they have successfully mastered the concept twice (time frame?), then they are good to go. Grading? Haven't thought of that yet. I was thinking more of a general holistic idea because realistically, maybe all kids don't get to all concepts twice. Maybe their final grade will include a percentage based on what they've shown .... but then I'm still saying that I'm okay with them not knowing things .... ARGH .... must ponder more.