Age - Any
Proficiency level - Any
Materials - as many identical sets of slips (with the tasks) as you want groups in your class.
1 - Prepare your set of tasks. You may choose to use the following kinds of exercises: fill-in-the-blanks; completion; definition; error correction; unscramble words/sentences; answer questions; ask questions to match the answers given; any other kind that may suit your purposes.
2 - Make one copy of the set of slips for each group.
3 - Cut the slips and mark each set with a different color (one group witll be blue, another red, another green, etc). You can draw a circle, a line, a heart, anything that will identify the set.
4 - In class, arrange the sets on your desks, far from each other to avoid mixing them up. Divide the students into groups of three. Number the students, 1, 2, 3. They will take turns performing three tasks: to get a slip with a task; to write the answer; to take the slip back for the teacher to check. The same student who returns the answered slip gets a new one (if the previous slip is correctly answered).
So, in the first round, student 1 will get the slip, student 2 will write the answer, and student 3 will take the slip back to the teacher. If it is correct, student 3 will get a new slip and take it to the group. Student 1 will write the answer and student 2 will take it to the teacher. And so on....
5 - You will check it and say "yes" (right) or "no" (wrong). If the answer is wrong, the student takes it back to the group and they try to fix it.They can only get a new slip if they answer the previous one correctly.