* Imagine all the windows and doors of the school are covered and you can't see out. You have to work out what the weather is like outside just by watching the children arrive in the morning. You want to know whether it is hot, comfortable, cool or cold. Is it raining and if so, is it raining heavily? You can't ask any questions. You can only watch the children coming in.
* You go into the classroom one morning and a camel is standing grazing on the plants on the window sill. Work out how it could have come in, then list the clues you would look for and any questions you might ask to confirm or disprove your idea.
In the film Finding Nemo, the story hinges on Nemo being able to travel from an aquarium tank back to the sea. It seems impossible, like some of the problems in the Sherlock Holmes stories. It's good to think of something impossible and then make yourself find a way of solving it. For example, you've left your lunchbox at home. You're not allowed to return for it. There's nobody in anyway, and you can't use the phone. But by lunchtime you've got it back. Work out how you did it. Now think of an "impossible" problem of your own and the solution.
* Draw a familiar scene from memory.
* Make up a quiz that tests observation. For instance how many windows are there in the classroom? Which way do the front doors of the school open? What does it say on the office door?
* This could be a group task. Write a short play about three children, called Sarah, Sam and Sunita, that you can put on in assembly. You are going to ask the people watching the play the following questions, so put the right clues in your play, but make them as difficult to find as you like.
Where has Sam been on holiday this year?
Which one of the three has a Gameboy?
What is Sarah's dad's job?
What is Sunita's favourite colour?
How many brothers does Sarah have?
Does Sam live in a house or a flat?
How does Sunita get to school?
What is Sam's best subject at school?
When is Sunita's gran's birthday?