These days there are different products with this slogan. For example, T-shirts, mugs, key rings, etc.
Click on the link below to read more about it and to create your own "Keep Calm and ..." slogan. Print it at home to decorate our classroom. Don't forget to use an imperative form to complete your slogan.
Keep Calm
Now you're ready for some activities about the imperative form
Imperative I
Imperative II