I first saw this classroom strategy in Diane Staehr Fenner and Sydney Snyder’s book Unlocking English Learners’ Potential avaiable in the UK here.
1-3-6 is a great strategy to develop oral language.
Give learners a disussion question or task to complete individually (1).
Then move to a group of (3) to further develop learners understanding of the question or task by talking about their responses.
Finally, two group of 3 join together to make a (6). In the group of 6 learners finalise their answers to the question or task and present these to the whole class.
The 3 steps involved in this classroom strategy promote lots of practice of using the target language and vocabulary, it also allows EAL learners that are new to English to hear good models of the language and allows all learners to deeepn their understanding of the question or task that you have set.