It's very rare that teachers get the opportunity to teach a debating class, at least in most middle schools. Most teachers who integrate debating will have a debate assignment or unit, varying in length from a week or so to a few weeks. There's a smattering of good commentary on this practice online -- check out Aquiram's reflections on The Great Debate and The Reflective Teacher's discussion on using debate in class, which you can read here.
A longer unit is possible for some teachers (depending on what subject you teach, of course, and how good you are at all the basic stuff like incorporating vocabulary and reading instruction into content learning (come on, is there really any other kind?) and process-based instruction that activities like debate require.
Over the last year or so, I've worked with a small number of teachers to develop ideas on sequencing for a twelve-week unit. I wanted to share it on the website for comment and revision. These things tend to work best if more people try them out and tinker - a kind of open-source unit plan, if you will. You can download it here. Comments, suggestions, and reports from the field are encouraged, either on this blog or via backchannel to me (kate[dot]shuster[at]claremontmckenna.edu).
The unit is designed for 60 days, with three debates for all students. It's annotated with relevant California English-Language Arts content standards in one column. If you're not in California, you can ignore these or match them up with your own content standards. Depending on the kind of class you're in and the topics you choose, you can add more standards met if you're choosing topics from the curriculum. (NOTE: to decode the standards abbreviations, CA's ELA standards are online here.)
The unit would probably be most easily accomplished using Middle School Public Debate Program (MSPDP) materials, including readings from our textbook Speak Out! Debate and Public Speaking in the Middle Grades, or the Teachers' Guide on our website, but could certainly be adapted for whatever format you wanted to use. I'm partial to the six-person debate format, as it involves a lot of students without getting too out of hand. It's also short enough for a class period, at 26 minutes, and dynamic enough for an audience to enjoy and pay attention to (though this is probably stretching it for most of the students we serve...).
I suggest that the unit be taught with a portfolio assessment system, which I discussed a few months ago here. You could use one topic, repeated three times, or several topics (I prefer this approach). The first topic should be easier. For ideas for debate topics for middle school students, we've got a giant list of topics we've used in competition here, and a list of topics synced with California's Social Science Content Standards here. Vocabulary can be taught as part of topic instruction and context-building for reading and research. I've included a persuasive essay as a final assignment - this probably won't work if you haven't done persuasive essays before, but the idea is for students to take a position on one of the topics and write a short essay in support of their opinion on that issue.
As for what the other students do while debates are happening, I suggest that some students be assigned to adjudicate each debate. They should be required to submit ballots and flowsheets as part of reporting for the adjudication part of the unit.
I suspect there will be much more discussion about the unit as people explore it, so I'll resist the temptation to go on and on about it. One teacher who used this last spring felt like it was too short. Another used it this fall and felt like it was impossibly long for the time allotted. So, as always, actual results may vary...