In normal years, when I teach in a physical classroom, I teach in sessions of ~90 minutes, with ~30 minutes break. This year, all teaching is done via Zoom (in real-time), and I wonder whether I should split each lesson into a larger number of shorter sessions, for example, split each 90+30 session into two 45+15 sessions.

On one hand, students are used to the standard 90+30 sessions; changing it might confuse them. Some students may e.g. forget coming back after the break, and this may cause a waste of time after breaks.

On the other hand, in remote learning, it is much harder for students to focus, so maybe they need more breaks.

Is there any research / experience regarding the optimal length of a remote real-time teaching session? Is it indeed shorter than classroom teaching session, and by how much?

  • 3
    @FedericoPoloni If it's a 4-academic-hour lesson, then yes, it's 90+30+90. There are also 3-academic-hour lessions, which are 90+30+45. Oct 12, 2020 at 10:55
  • 1
    Are students considered to be "in class" during the break? Or are they two separate classes back-to-back. I ask because That half hour time may not be yours to claim back anyway. Oct 12, 2020 at 14:10
  • 7
    Relevant: "Zoom Fatigue" - nationalgeographic.com/science/2020/04/…
    – henning
    Oct 12, 2020 at 14:12
  • 5
    @ErelSegal-Halevi Well them I would definitely recommend not doing 90/30/90 in any situation. Ninety minutes is too long to focus and half and hour is too long to stay on topic. I'll leave the answers below because I like them. Oct 12, 2020 at 16:55
  • 2
    More on Zoom Fatigue. This might merit its own question.
    – livresque
    Oct 13, 2020 at 5:02

2 Answers 2


If you search using Google or another search engine for something like "research on maximum effective lecture time" you will get some ideas. In general, long lectures are less effective than short ones because of the student's attention span. Video lectures should be very short, say 10-15 minutes for effectiveness. And with required activities at the end of each short session. So, a long "lecture" can be presented as a sequence of short but complete segments. Real time is a bit different, but keep all of that in mind in course design.

But it really depends on what you and the students are doing in the given time period, rather than the length itself in any absolute sense. A talking head writing on a board or (worse) showing a bunch of slides gets old and boring very fast. If the students have a chance to break it up with questions or some problem solving activities it is better and the class-period can be longer and still effective. Class discussion sessions is another way to break the monotony, but harder online and nearly impossible with video unless there is an effective communication channel shared by every student.

I used to teach a couple of courses that lasted all day and only met once a month. But the face time was usually broken up into small segments and we used very effective, but simple, communication tools so that students could "engage" with the course and the instructors (two of us) at any time through the period between face-time sessions.

The key is to keep the students active and engaged. Once they lapse into passivity you are lost. Some students have the skills and background to keep themselves engaged in sub-optimal environments, but not all do. Perhaps not even the majority.

  • 4
    10-15 Minutes? This may be the average attention span of people watching shopping haul videos on YouTube and be the optimal video length to maximize ones viewership as a YouTuber. I think one can certainly ask more of us students though. Especially in technical subjects. 90 minutes of concentrated work is a skill which can be expected, even in the "faster and faster " (digital) age.
    – user117200
    Oct 12, 2020 at 20:12
  • 6
    @TheoreticalMinimum, actually there is research on that point, but I've forgotten the source. It is mentioned in another post on this site. Video is too passive. For example, you can break up an hour math session according to the theorems introduced and proved. One per session. Most won't require even 15 minutes if done well. If well labelled they are easy to return to for review, rather than scanning a long video.
    – Buffy
    Oct 12, 2020 at 20:16
  • 11
    @TheoreticalMinimum, no the goal is not to reduce the total engagement time, but to chop it up into semantically meaningful chunks.
    – Buffy
    Oct 12, 2020 at 20:21
  • 1
    Yes, he was very human and tried to make the lectures as informal as possible. "Welcome to my office, this semester is going to be different, just you, me and my blackboard!". But he didn't do comedy. And important: He had a good camera. I think good old methods like teaching on a blackboard are not per se bad, often they are just done bad. Look at the Feynman lectures e.g.! Me and a lot of students in my direct environment don't like too "fancy" teaching methods. This makes me feel like I'm a small child that needs to be nudged into focusing or learning. But now I'm getting off topic.
    – user117200
    Oct 12, 2020 at 20:28
  • 1
    Its not just shopping videos on YouTube. This analysis from EdX (one of the biggest providers on educational video online) shows that students stop learning after around 6 minutes. blog.edx.org/optimal-video-length-student-engagement Oct 12, 2020 at 22:03

No research here, just a small amount of experience to chip in. :) And no answers, just observations...

First, they're coping with many changes that roll in on the news daily or weekly, many of them more of an upheaval than taking the same number of instructional hours and cutting it into smaller blocks. I don't think you should decide based on unfamiliarity in COVID times.

In my experience, your intuition is right: 90 minutes is a long time to be continuously focused on Zoom, but 45 minutes is very doable. Worse, many people (try to) multitask during remote learning, and 90 minutes is a long time to be dividing attention.

On the other hand, I think a longer break is a good idea. Students seem to find it hard to really break on Zoom. They turn off their mic and video or run to the washroom, but it's hard to do the necessary dissociation: standing up, moving their legs, bustling and talking and sharing impressions with peers, getting a breath of fresh air. If they stare at a screen during break, they won't come back with a fully refreshed ability to sustain attention for another block. For this reason I suspect that 30 minutes of break with explicit reminders to get up and away from the computer is more useful than 15 minutes. But 15 is better than 10 and 10 is better than 5.

As for coming back late and wasting time: not your problem. It's no different from deciding to get a snack and wander luxuriously when learning in person. If they're not back on time, the lesson doesn't stop for them.

How about the problem of momentum? Four blocks with three breaks between them is pretty significant as far as stopping and starting. You would need to be very much on point and purposeful to avoid transition/inertia eating into the 45 minutes from both sides.

One idea is to designate each 45-minute block for a different purpose. For example, if all four are direct instruction, the repeated pattern will accentuate the dreaded feeling of sameness. "Is this the third block or the fourth? Did he teach us that earlier today or last week?" Whereas if you teach the first 45-minute block, give them exercises the second one, teach the third, and give them exercises the fourth, that's quite a nice rhythm.

The same strategy also helps mitigate a 90-minute block. Being present and working while the instructor supervises / is present for questions is not taxing; what's taxing is being attentive while the instructor talks and shows slides (on a screen you may not be viewing or have snapped to half of the screen).

  • I challenge the "45 min is very doable" assertion. I think for delivery content in a lecture in real life 45min is the absolute limit. On zoom I don't think it still works because the intensity of the other person being in the same room is missing. Oct 12, 2020 at 18:01
  • 3
    Yes, I would agree that 45 minutes of uninterrupted instructor speech would still be very taxing. But 45 minutes on Zoom with some speech, some reading, some diagrams, some discussion, and other (hopefully) normal varied lecture stuff is OK for most, I think. Oct 12, 2020 at 20:04

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .