Collaboration increases the opportunities a student has to use the target language, and thereby develop their skills in it.
Example
The task-based learning approach requires learners to work on collaborative activities.
In the classroom
Learners can benefit from collaboration in a variety of activities, including writing tasks, projects and inductive approaches.
Further links:
https://www.teachingenglish.org.uk/article/unit-9-task-based-learning
https://www.teachingenglish.org.uk/article/task-based-speaking
https://www.teachingenglish.org.uk/article/working-pairs-groups