There is a suspicious-looking A4-sized envelope on my table. What makes it suspicious are the words "TOP SECRET" written in big red letters on the front.
I pick it up and carefully examine it in front of my fellow spies, who are cunningly disguised as schoolchildren. At a signal - well, several signals actually - they fall silent. Suddenly the atmosphere is tense and claustrophobic. I feel like George Smiley in a scene from Tinker Tailor Soldier Spy.
I ask Ryan - a trusted agent and reasonably proficient reader - to open the envelope and reveal its contents; explaining that I may have to kill him afterwards. He is undeterred. Inside the envelope is a note, which he reads aloud: "Enclosed is a list of passwords used by enemy spies. The list is encrypted. To decipher the passwords you must use the secret code. The secret code is in the place where the fat animal sleeps."
Below the message is a list of patterns made up of gridlines and dots. We blow these up on the interactive whiteboard and discuss what they might represent. For a few frustrating minutes we are unable to make any sense of them.
Ryan reads the cryptic last part of the note again: "The secret code is in the place where the fat animal sleeps." It takes a while but we finally arrive at the term "pigpen". "Wait, agents," I whisper. "If I remember correctly, back in the early days of my training at GCHQ we learned about something called the pigpen cypher. It is a code that substitutes letters for symbols."
Just by chance I happen to have an example of a pigpen cypher on the very next page of my interactive flipchart. For 20 minutes my classroom is as intensely productive as a scene from Spooks (only without the explosions) and it doesn't take long before the code words are revealed. But what an odd set of code words they turn out to be. And isn't it strange how so many of them have featured regularly in our spelling tests?
Deciphering words children find difficult to spell is a great way to practise them. Especially when - in true MI5 fashion - each word must be committed to memory. The original paper copies are destroyed to prevent them falling into enemy hands. Now only those who can prove their ability to successfully memorise the spellings of their passwords are allowed to go on to the ultimate challenge, which is to reveal the name of the top-level infiltrator operating in our school.
"Who?" I gasp, incredulous at their findings. "I always knew our head was up to no good. Now, which of you is licensed to kill?"
Steve Eddison is a key stage 2 teacher at Arbourthorne Community Primary School in Sheffield.
There are lots of codes children can use to decipher secret words and messages. Have a go at making cypher wheels and try out the Caesar cipher, which involves letter substitution.
Create an air of mystery in the classroom and get pupils to use newly learned words in their own detective story with streetno9's resource pack.
IN THE FORUMS
English teachers are talking about mnemonics. Which ones do you use in your classroom?
Find all links and resources at www.tes.co.ukresources049.