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Gallery of
Classic Mistake
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Maths posters
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How on earth can posters of mistakes help with teaching maths?

The full series of Classic Mistake posters have been on display in the Maths classrooms and corridors of my school since 1997. At the time, some staff had concerns about them "sending out the wrong message" by showcasing incorrect maths, but such worries have proven unfounded.

In fact, the whole concept appears to have been embraced by everyone and students often joke with one another about avoiding "the Classics". It's okay to make these mistakes once, but they shouldn't keep making them. Awarding them a "I made a Classic Mistake today" sticker also helps to reinforce in their minds each of these avoidable errors (see the
Freebies page to download these stickers).

And how many posters do you currently have up in your classroom that actually require the reader to think about what they are looking at? Many a visitor to my classroom has either been intrigued to find out what was wrong with the poster they were looking at, or they have taken great pride in having spotted what was wrong with it.

On a more anecdotal level, there has been a school five-a-side football team who called themselves "Classic Mistake Number 5", some of our students leaving for University asked for their own copies of the posters, and in 2006 the Sixth Form Revue even contained a short movie sketch whose punchline included the phrase "Classic Mistake Number 1". Proof of the impact that they could also make in your school?


What are Classic Mistakes?

A mistake in Maths earns "Classic Mistake" status if it is regularly made year in, year out, by successive classes of pupils or students, in classrooms.
They even get to the point where teachers will often incorporate Classic Mistakes into their lessons as teaching points.
If the students know where the pitfalls are, then they have a better chance of avoiding them - well, that’s the theory at least!

Where have they come from?
Mainly from marking exam scripts, and observing which errors were most prevalent.
Some have been suggested by students.
Others have arisen from sheer teacher frustration!
If you have a suggestion for a new Classic Mistake poster, then just make

What’s the Gallery all about?
In the Gallery you can see at a glance each of the Classic Mistake posters and download a single copy of either a colour or black and white poster.
Also you can listen to the mp3 audio file that accompanies it, or download it for listening to later.

What are the mp3 files?
They are mainly the verbal explanations that might be given to students who can’t spot what the mistake in each poster is.
They are presented here in the style similar to many podcasts that are already available on the Internet - bit of music, bit of chat and ending with a bit of music.
The 41 audio files that accompany the original 41 posters were created over a period of 8 months, from November 2006 to July 2007. That's an average of one every 6 days!
If you're a teacher, why not use the posters and audio files in your lessons - it's one way of changing the pace of revision lessons.
The audio files can also be accessed as podcasts. See the
Podcast page for more information.

Wow, there’s tonnes of stuff here!
Yes there is.
There are currently over 170 posters on this website that you can download, print off and decorate your maths classroom, maths corridor or whole school with!
Encourage your students to visit the website, check out if they can spot the mistakes in each poster, listening to the mp3 commentary if they can’t.
Better still, have them subscribe to the podcast, so they can download the mp3 files to whatever portable audio player they have and they can listen to them on the move … and everyone will assume that they are only listening to music!
Check out the
Links page that directs you to other podcast sites, if you’re into that sort of thing.

How did you create this website, and all the stuff on it?
All the posters were created in Microsoft Publisher and converted to pdf format using Adobe Acrobat.
The .mp3 audio files were created using
Audacity via Sennheiser PC155 headphones with microphone.
The sound effects used in the podcasts were found
here and here whilst links to the music artists' websites are on my Podcasts page.
I've also recently been notified of a great new website for even more sound effects, at Sound Snap.
Various websites were trawled to find the javascripts required to make this website work the way it does.
A Quicktime Player Plugin detector in javascript came from
The pop-up window that displays large images whilst also playing the mp3 came from
A tutorial on how to use Cascading Style Sheets was found
Helpful websites about creating podcast feeds were
here and here.

Who are you?
My name is Nevil Hopley and I am currently Head of Maths at a large independent school in Edinburgh, Scotland.
I've been teaching Maths in classrooms since 1993, creating websites since 2003 and maths podcasting since 2006.

I also have my own company that sells software for TI Graphic Calculators to schools. Click here to find out more.