Extension tasks can provide more, or different, forms of practice. They can also make classroom learning more meaningful, as they give learners a chance to personalise language and content.
Example
The learners have been reading about extreme sports and as an extension task they research other examples, choose one to explore further, and present their findings to the group.
In the classroom
Extension tasks can be a useful strategy to deal with mixed ability classes, as they can be given to early finishers or set as extra, more demanding work for higher level learners.
Further links:
https://www.teachingenglish.org.uk/article/managing-young-learners
https://www.teachingenglish.org.uk/article/shakespeare-extension-activities-kids
https://www.teachingenglish.org.uk/article/extension-activities-shakespeare-lesson-plans