New technologies come and go but some hang around decades after introduction. For example, the late-19th century chalk blackboard in classrooms morphed into current white (or green) boards.

Consider the overhead projector (OP). While many teachers' rooms have projectors mounted on ceilings that project Internet images onto whiteboards, just as many teachers have a cart with an overhead projector handy. And even in a desk drawer stacks of transparencies (older readers will nod their heads in agreement but rookie teachers may scratch their heads in puzzlement over just what are transparencies).

So here's what has happened to a once innovative technology for one generation of teachers to become a ho-hum old technology to a later generation and a head-scratcher to brand-new teachers in 2021.

When were overhead projectors introduced into classrooms?

A 3M employee invented the machine in the early 1960s and within a few years, it had become a tool that more and more teachers relied upon to project new information and concepts onto classroom screens or green- and white-boards.

What advantages and disadvantages did this "new" technology have over chalk boards?

The advantages are clear. Using transparencies, teachers could outline a lecture beforehand with bullet-points and simply show it on the OP or as she moved through the presentation, project new information, write out questions and still monitor the class. Watching students and seeing which ones are inattentive or off-task is a crucial part of classroom management essential to teaching the content and skills embedded in the teacher's lesson. When a teacher writes on a black- or green-board, she has her back turned to class as she puts items on the board. Also missing from teaching a lesson to 25-30 students using blackboards is chalkdust or smeared hands from markers on whiteboards.

The disadvantages of using the OP is that the teacher remains in a fixed position in front of the room and cannot move around the room to check on students' note-taking or inattentiveness. She has to conduct a whole group discussion while going over the transparency although small group activities can occur during the presentation or when the OP is turned off.

More often than not, a mix of using OP and chalkboards in lessons still occurs.

Classroom example of OPs being used in lessons

Over the last year or so I’ve been (unofficially) mentoring a third grade teacher at my school. One day she called me to her room and asked if I would take a student out of her class because his behavior was causing such a disruption. She had enough of his nonsense. So I went up to her room, asked him to come with me and I gave both the student and the teacher a break from each other. 

I brought the student into the computer lab and I asked him what he thought the problem was. After listening to his story, I was wondering if there wasn’t enough blame for both parties to share. Sure enough, after he had calmed down and told me that he was ready to return to the class, I walked him back upstairs. When I walked in the room I noticed that the class seemed to be up for grabs. Some students were talking to each other, some students were just sitting at their desk drawing. Others were vying for the teacher’s attention through a variety of methods. In short, the teacher was having one of those days. 

We all have them. I certainly do. 

She looked at me with a look of exasperation and said, “What can I do?”

It was clear to both of us that she needed to work on her classroom management skills. So I asked her if I could try something with her class. “Anything,” she replied.

I asked her where her overhead projector was. Apparently it was gathering dust in a corner. I dragged it out, plugged it in and quickly got the kids to shuffle their desks so they could all see the wall where I was going to project the screen. I grabbed a blank transparency to write on and put a quick heading down for them to copy. Shockingly, the kids looked at me like I had just put an Algebra equation up for them to solve. So I explained what a heading was. The great thing was that as I was talking, I could face the entire class while demonstrating the heading on the wall. Not only that, but the projection was large enough that no matter where you sat in the room, you could see what I was doing. 

As I taught, I could see the light bulb go off over the teacher’s head. She learned what some of us already know: the overhead projector is a great teaching tool as well as a powerful technique for maintaining order in your classroom.

Why are OPs much less used today

Newer electronic technologies have usurped OPs just as videocassettes and TV monitors replaced movie projectors and films. For OPs specifically, the document camera and, later, laptop computer with an ceiling fixture could project video clips, Internet information, and whatever else the teacher had planned for a lesson.