All you need to do is just print the extract out and read it to your class. See if they can work out what genre it is. This is a useful way to start or end your lesson.
Why not come back regularly and collect the extracts?
 
This extract has been taken from Writers' Lives by Dennis Hamley.

Roald Dahl

Roald Dahl was born in Wales of Norwegian parents. When he died in 1990 he was one of the best known of all children's authors. Despite the fantastic imagination that was to create Charlie and the Chocolate Factory and The BFG, Roald Dahl did not get on well at school: we know this from his autobiography Boy.

Dahl became a writer during the Second World War. He was a fighter pilot, even though he was so tall that he could hardly fit into the aeroplane's cockpit.

This book is part of The Pelican Big Book series.
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Can any of your class Spot the Genre? (A Biography.) Have any of the children in your class read Roald Dahl Books before? What is an autobiography? What was the name of Roald Dahl's autobiography? You could encourage the children in your class to write short biographies of their lives!