To begin with, I am not aware of any reliable statistics. I can only draw on my personal experience and summarize a number of related Google search results.
It is obvious, I hope, that it is impossible to spend more than 3 clock hours talking without a break. I guess that’s the maximum. As for the minimum, an online lesson can be as long as a regular phone call, i.e. it can last for as little as 5 or 10 minutes. Personally, I like it when lessons are 2h15min long, with a short break or a longish filler activity when 2/3 of the time has elapsed. But I cannot justify my preference with reference to the literature, because there is nothing in the literature:( apart from some “circumstantial” evidence.
Let me elaborate on that. First and foremost, a language lesson like an aerobics workout should start with a warmer. Most warmers allow the student to practise making some small talk, discuss the latest news and learn a few related lexical items, ask questions about the last homework assignment and the like. It is an important element, though I can think of situations when you can opt out of it and “get down to business”. The usual recommendation is for a warmer to last between 3 and 10 minutes, the average being 5 (without homework questions!).
The rest of the lesson is usually comprised of activities. Again, most activities are composites, i.e. they are made up of several parts or stages.
Stage 1 is known as lead-in. It introduces the topic or activity and usually takes between 2 and 15 minutes in an onsite lesson. It is impossible to give a more precise estimate, because you have to consider the number of the students present, their level, motivation and familiarity with the topic.
Stage 2 is really a meta-stage, but it must never be ignored, because it has a direct impact on how successful the activity itself will be. You tell your students what they have to do or set the task during this stage. You may have to demonstrate, model, elicit sample answers and so forth to make sure your students understand what they have to do and how. Timewise, this stage lasts between 1 and 5 minutes on average, and depends on the complexity and focus of the activity.
Stage 3 is frequently labelled run in lesson plans. It is the activity per se. During stage 3 your students usually do the task, and your role is to monitor. In 1-to-1 lessons the teacher usually forms a pair with her student and does a double load of work, i.e. does the task and monitors simultaneously. Whether 1-to-1 instruction is the best way of teaching speaking is a controversial issue. I for one have my reservations, but outlining them is beyond the scope of this post, so I’ll leave it at that. This stage can last between 5 and 90 minutes.
Stage 4 is another meta-stage that is often labelled close in lesson plans. The teacher tells the students that their time is up and rounds up the activity. Sometimes it is necessary to stop the activity before it has come to a logical conclusion, before everything has been done or all the questions have been discussed. You have to tell your students whether they will finish the activity later in a subsequent class or for homework, or whether that’s it and no more work is necessary. Whatever you decide, you have to make sure that the students are not frustrated and can see the pros of your choice. Of course, it is great when you are very good at timing and can estimate how long an activity will take to the minute. I have to admit it that I still have to work on that:( and it is not uncommon for me to underestimate – I never overestimate – the time necessary to complete a task, as a result of which I occasionally have to do without some or all of the follow-up activities. Closing the activity and telling students whatever next usually takes 0.5-5 minutes.
Stage 5 is usually the time when you provide different types of feedback. Providing activity feedback such as the correct answers normally takes 1-3 minutes. Providing delayed feedback to do with the mistakes that you jotted down while your students were doing the activity might take up to a quarter of an hour.
Stage 6 is any follow-up activity or task that is based on the main activity. In other words, it is a new activity that might take as long as stages 1-5 combined or as little as 3-5 minutes. What makes it a stage as opposed to a standalone activity is its dependence on the outcomes and language practised during the main activity. It is not unusual for an activity to be followed by more than one follow-up task.
Now let me do some simple maths.
If a lesson is comprised of a shortish warmer and a short activity with a tiny little follow-up task, it should take you a minimum of
greetings 1 min
warmer – 3 mins
lead-in – 2 mins
set task – 1 min
run – 5 mins
close – 1 min
feedback – 2 mins
follow-up – 3 mins (set – run – close)
feedback – 1 min
leave-taking – 1 min
GRAND TOTAL: 20 mins
As can be seen from the estimate above, it is possible to have an even shorter lesson – 10-11 mins – if you decide to do without politeness conventions (i.e. if you choose to say neither hello nor goodbye and start doing the main activity immediately), warmers (it is possible if the student is fairly advanced and has plenty of speaking practice outside class, which usually means that he doesn’t really need to “warm up” making small talk) and follow-up tasks. But would such a lesson be as efficient? I am not sure.
Another consideration is that stage 3 of most enjoyable speaking activities takes between 15 and 40 mins on average (most fun speaking games take at least half an hour to play because there are usually several rounds, and some communicative games last for an hour and a half), and the higher the student’s level is, the longer the activity tends to take. You should also allow for some thinking time. Not all speaking activities are heated discussions by nature. Nor are they tongue twisters – it is neither your nor your students’ objective to speak as fast as you can all the time, but it never hurts to introduce time limits.
What I’d like to make clear now is that the framework described above pertains to different kinds of language learning activity, not only collaborative speaking tasks. Students may have to not only speak, but also listen, write, read and do hybrid tasks in class either alone or in pairs or small groups. The nature of the task set as well as all the student variables have to be considered when estimating the time the lesson you plan might take.