Yesterday, I did a speaking test for 200 students. It's quite a big job and took me all day. But it would have taken much longer if I had never done this before and if I wasn't organized.
Some teachers allow students to choose their partner and choose their subject. Sometimes they can do this days in advance. Consequently, some students will find a dialog and memorize it and then perform it for the test. I don't do it this way. I don't think it's very realistic.
In the workplace, people need to be able to speak English to anyone and they can't always choose the topic. So I tell my students they can choose any partner they want as long as student #1 chooses students #2 and student #3 chooses student #4, etc. I tell them they can choose their own topics to talk about. They come up to my desk and choose from several slips of paper which are facing down. The students cannot look at the paper before they choose. Consequently, they are choosing randomly. I do allow them 3-4 minutes to prepare before the interview. The topics are always things that we practiced discussing in class.
When one pair of students sits down to do their dialog for me another pair of students will come up to the desk, choose a topic and stand aside to prepare. I don't allow them to use dictionaries, notebooks, textbooks or to talk with other students during the preparation period. I sit facing the two students who are talking but behind them I can keep an eye on the next two students who are preparing for their talk. This is important because they many of them can hardly keep themselves from a bit of cheating if it is possible.
The students talk to their partner on the topic. I used to be an IELTS examiner and found it is a bit extra work to have to also be asking the students all the questions. So I like to get the students talking with each other and I listen in. If I think a student can go higher or if their dialog was too short I will jump in with a few extra questions.
While they are talking I am recording them. They hold a cheap $2 clip-on microphone that I found which works really well and is fastened at the end of a ballpoint pen. I use free program called Audacity to record the interview. Although I'm sitting right next to them, I actually listen to the students through a set of earphones. This ensures that everything is being recorded. The interview is recorded for reference in case I want or need to go back and check something or if I need to justify a score I have given.
If their dialog is too short or doesn't reveal their English skills well enough I will ask some questions to make them speak more. Answering"why" questions or questions where they have to explain or justify a viewpoint are some of the toughest questions and are good to push students to the limits.
I have some band descriptors and a list of all the students names and numbers on an Excel sheet. The band descriptors are divided into three areas of speaking (communicative range, overall fluency, accuracy & appropriacy) and four levels (levels 4-7 of a 10 level rating system) While they are talking, I scan the band descriptors and give them an initial score. I continue to listen to them and modify parts of my score as they perform better or worse.
It's very important to have a clear set of standards that the students should speak to. And while they are speaking you should be constantly checking those standards and try to measure the student to those standards as best you can.
After all of the testing is done, I will use Excel to average out the band scores and assign grades on a curve.