Comparing two conventions: erase when you finish teaching, or erase when you begin [closed]

Question

I feel like there are two reasonable conventions when it comes to board etiquette for when to erase.

1. Everyone erases the board before they start teaching.
2. Everyone erases the board after they finish teaching.

Benefits of (1):

(a) Convenience for students: You can leave your writing on the board for students who want to study it after class.

(b) Stability: You're always forced to erase before you start anyway, so nobody gets disadvantaged if someone fails to erase before them.

Benefits of (2):

Honestly the only benefit I can think of is: If you're rushing to class and barely make it by the start time, you don't want to delay class by spending the first 1-2 minutes erasing. However, this doesn't seem like a real benefit, since if you abide by (1), then you're also saving 1-2 minutes at the end of class, allowing you to get a jump on your next task.

Somehow, (2) seems like the standard etiquette, to the point that many professors get upset if the board isn't empty when they arrive. However, it doesn't seem especially logical to me. What arguments are there for (2) that I haven't considered?

EDIT: At this point we already have a lot of interesting answers, but if anyone is curious, I initially asked this question from an informal policy point of view — I.e., which convention, if adopted by most people, would make the community better off as a whole? Another minor clarification — I was thinking of blackboards, but it’s an interesting point that dry erase markers get harder to erase the longer they remain on the board. IMO this tips the scale towards favoring (2) for whiteboards. For blackboards I still feel that (1) is better.

Answer 1

I very much prefer option (1) as a general blackboard cleaning policy, mainly for the reasons mentioned in the questions, but there are some other points:

• Efficiency: Where I am, cleaning staff cleans the boards once a day, so that they are clean for the first lecture of the day. If the last person a day cleans it, the staff will clean it again unnecessarily.

• Standards: Other people may have very different interpretation of what a "clean blackboard" is and I have seen a lot of "cleaned" blackboards which we not at all clean by my standards. When cleaning before class, everybody has a blackboard meeting their own standards.

A minor point (which I still like): Finding a blackboard full of stuff from the previous lecture gives me some impression of what else is going on at my place, it may give me opportunities to approach the person who lecture before me and chat with students about what is still there.

Experience from where I taught: In math (and partly in CS) people realized that (1) is the superior approach, all other departments were (sometimes strongly) insisting that (2) has to be done (without being able to explain why except for "that how it should be be, period").

Answer 2

Please clean up your own mess

You could just as easily broaden your enquiry to cleaning up any resource that is used by multiple people in a communal fashion. Should I put my rubbish in the bin, or just leave it on my table for the next person to clean up prior to their own use? Should I wipe up my spilled coffee on the tabletop in the office kitchen, or leave it to the next person to clean up prior to their own use? Should I use the toilet brush after doing something foul in the gymnasium toilet, or should I leave it to the next person to clean up prior to their own use?

To ask these questions is to answer them --- mature adults clean up their own messes. While there may be some tenuous marginal benefits from the contrary practice as it pertains to a whiteboard, it falls within the same general ambit of being rude. Whilst the same amount of total cleaning obtains in either case, leaving your mess out for the next person to clean engenders the general "enshitification" of society.

Answer 3

I admit that I am firmly in camp (2) --always erase at the end and leave a clean board for the next class. But I also recognize that I'm sure some of that is just "the way we've always done it."

I like the simplicity of knowing I'll be starting class with a clean slate (sorry, couldn't resist). As I am coming into the room, I have my laptop to set up, homework/exams/whatever to pass back, maybe students coming up and asking questions, whatever. Prepping the board is something I do not have to worry about -- and so I can also do that final "did I get the handouts off the printer," etc run through in my head. The professor leaving at the end of class, in general, will have fewer of these -- and is not about to start teaching; or, if they are, they'll be walking to their next classroom where the clean board there will give them the ~30 seconds or whatever to get in the headspace to start class.

However: One good argument I can make for (1) is the serendipity that often occur on an un-cleaned board:

• One semester, I was teaching Calculus II right after someone else was teaching Combinatorics. By luck one day, they had been talking about formal power series and generating functions right as we were starting Taylor Series. As my students came in to Cal II, a few had questions and I gave the short 3 minutes of "it turns out these are much more powerful than just a way to approximate sin(x) as a polynomial."
• Likewise, when I am teaching back-to-back in the same room, especially when I'm going from more advanced to more intro level classes, my new students will filter in before I have a chance to clean the board and sometimes this leads to interesting questions.

Answer 4

I think @Lars Seme's answer captures my sentiments already pretty well, except that I would add the following argument:

Let's just all be good humans and do something nice for the person who comes after us, by cleaning the board for them.

There already isn't enough kindness in this world. Chances are that the person coming after you is in the same department, and will be grateful for the act of kindness.

Answer 5

I've been erasing before-and-after for decades, and counting on allowing time for it. Once-upon-a-time I tried to argue with people about whether they should erase (or not) at the end of their classes (before mine), but that proved to be a waste of time, or, worse, a waste of time and having people yell at me about their privileges.

It's not only "erasing", but turning off the computer projector, raising the screen, and lots of other stuff...

Btw, it's not at all good to wash blackboards every day, because that takes away the pore-filling "seasoning", making it harder to erase, etc.

Answer 6

What is the culture of your institution?

This is, in my experience, very much a matter of institutional culture. In the mathematics department where I earned my BA and MS, the culture was very much of type (2): you were expected to erase your board when you finished teaching. If you did not, you were likely to have someone complain to the chair of the department, and then get a stern talking to.

On the other hand, at my PhD institution, the culture was of type (1): instructors wandered into class a minute or two before the start, erased whatever was on the board, and taught their class, then wandered out, leaving whatever was up on the board for anyone still taking notes. This was expected, and no one complained about boards not being erased.

And then there is type (3): at my current institution, most instruction takes place at a distance. I will typically have two or three students in the classroom with me, and many other students in other classrooms across our service area. My "board" is a large touchscreen at the front of the room (a SmartBoard, specifically). There is nothing to erase, neither at the start of class, nor at the end of class! Yay!

Erase the board at the end of class, anyway...

All of the above having been said, I always erase my boards when I am done teaching (again, I haven't had to bother since getting to my current institution, but...). If you are at an institution where the culture is of type (2), you are expected to do so; and if you are at a type (1) institution, no one is going to complain if you leave the classroom with clean boards.

I would rather walk into a classroom with clean boards so that I can get started right away. Moreover, if I come in on Monday morning after someone taught on Thursday night, it is very possible that the board is going to be harder to erase (dry erase markers get harder to erase the longer they are on the board), and I am going to get a bit annoyed about having to really scrub the board or track down some board cleaner. I think that it is a small kindness to the person who needs to use the classroom next if you clean your mess up before they arrive.

Regarding the idea that students may still be taking notes: they can pull out their smartphones (even my students, many of whom don't have running water or electricity at home, all seem to have smartphones...) and take a picture. Or get a copy of the notes from someone else.

Answer 7

Frame challenge: Don’t clean the board yourself

Rather, it should be your students that clean up when they don’t need your notes anymore. This can be right at the end of the lecture, or while they discuss with you afterwards, or after you left, or before you come in, or even as you are about to start your lecture.
Whatever suits them and lets you use the board is fine.

Now of course this depends on your students cooperating. Hopefully you have a good relationship with them and it just works. A simple means to get them motivated is just not to start until the board is clean and cut into Q&A time to compensate.
Or do it as one (in-) famous lecturer here does: Every new batch of students would miss cleaning the board once - and only once as he would just write on the dirty board anyway. After all, the writing was for the students, not the lecturer.